LISTEN TO THE SCIENCE, PEOPLE!

[thelivyjr]

“CLIMATE, HISTORY AND THE MODERN WORLD,” Second Edition by H.H. Lamb

VARIATIONS OF THE CIRCULATION AND HEAT DISTRIBUTION IN THE ATMOSPHERE AND OCEANS

Much less can be said about the internal variations on time-scales from weeks to years in the heat economy, and the evolutions in the circulations, of atmosphere and oceans.

Most meteorologists believe it necessary at present to treat these in relation to longer-term forecasting as random in their occurrence.

There may nevertheless be some natural oscillation periods, such as one of thirty days (or very close to one month) which is prominent in the weather variations during the winter half of the year in middle latitudes of the northern hemisphere.

Hints have been found of associations with (a) various shorter-term cycles of solar activity, (b) variations in the tidal pull of the planets on the sun as their alignments change and which may have some effect on disturbances of the sun, and (c) cyclic variations of the combined tidal force of sun and moon acting upon the Earth and its atmosphere as well as on the oceans.

The varying activity of solar disturbance may itself be partly associated with the (predictable) tidal pull on the sun of the planets as their positions vary.

The likely period lengths are in many of these cases known but the correlations appear to be weak and unlikely to serve as a practicable basis for forecasting.

There may be an exception to this in the case of the complex of small wanderings of the Earth’s rotation axis (and hence of the poles) that are known collectively as the Chandler wobble.

This wobble is presumably related to readjustments of angular momentum (the momentum of spin) and of inertia between the solid Earth, and the fluid elements of its interior, and the atmosphere and oceans, at least partly under tidal forces.

The components of the wobble include an annual cycle of displacement of the poles by a few metres and oscillations of other period lengths ranging from about thirteen to fifteen months.

Several scientists in the United States and in Russia, notably I.V. Maksimov of the Main Geophysical Observatory, Leningrad, have been interested in the possible usefulness of the wobble in weather forecasting, since even such small displacements of the pole may produce enormously bigger displacements in the atmospheric circulation.

This is because of the effect of any momentum exchanges between the massive Earth and its thin atmospheric ‘skin’.

Lately Bryson and Starr in the United States have succeeded in resolving the wobble into discrete components, which facilitate prediction of it and seem to show useful associations with global weather development over some years ahead.

MEDIA RELATIONS OFFICE

JET PROPULSION LABORATORY

CALIFORNIA INTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

http://www.jpl.nasa.gov

Contact: Rosemary Sullivant (818) 354-0474

FOR IMMEDIATE RELEASE: July 18, 2000

A MYSTERY OF EARTH'S WOBBLE SOLVED: IT'S THE OCEAN

The century-old mystery of Earth's "Chandler wobble" has been solved by a scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

The Chandler wobble, named for its 1891 discoverer, Seth Carlo Chandler, Jr., an American businessman turned astronomer, is one of several wobbling motions exhibited by Earth as it rotates on its axis, much as a top wobbles as it spins.

Scientists have been particularly intrigued by the Chandler wobble, since its cause has remained a mystery even though it has been under observation for over a century.

Its period is only around 433 days, or just 1.2 years, meaning that it takes that amount of time to complete one wobble.

The wobble amounts to about 20 feet at the North Pole.

It has been calculated that the Chandler wobble would be damped down, or reduced to zero, in just 68 years, unless some force were constantly acting to reinvigorate it.

But what is that force, or excitation mechanism?

Over the years, various hypotheses have been put forward, such as atmospheric phenomena, continental water storage (changes in snow cover, river runoff, lake levels, or reservoir capacities), interaction at the boundary of Earth's core and its surrounding mantle, and earthquakes.

Writing in the August 1 issue of Geophysical Research Letters, Richard Gross, a JPL geophysicist, reports that the principal cause of the Chandler wobble is fluctuating pressure on the bottom of the ocean, caused by temperature and salinity changes and wind-driven changes in the circulation of the oceans.

He determined this by applying numerical models of the oceans, which have only recently become available through the work of other researchers, to data on the Chandler wobble obtained during the years 1985-1995.

Gross calculated that two-thirds of the Chandler wobble is caused by ocean-bottom pressure changes and the remaining one-third by fluctuations in atmospheric pressure.

He says that the effect of atmospheric winds and ocean currents on the wobble was minor.

Gross credits the wide distribution of the data that underlay his calculations to the creation in 1988 of the International Earth Rotation Service, which is based in Paris, France.

Through its various bureaus, he writes, the service enables the kind of interdisciplinary research that led to his solution of the Chandler wobble mystery.

Gross's research was supported by NASA's Office of Earth Science, Washington, D.C.

JPL is a division of the California Institute of Technology in Pasadena.

https://www.jpl.nasa.gov/news/releases/ ... obble.html

[thelivyjr]

MIT TECHNOLOGY REVIEW

Earth's Chandler Wobble Changed Dramatically in 2005 - New analysis shows that the Chandler Wobble in Earth’s axis changed phase by 180 degrees in 2005. The question is why.

by Emerging Technology from the arXiv

Aug 31, 2009

If you travel to the Arctic and attempt to find the axis of Earth’s rotation, you’ll notice something odd.

The position of this axis on Earth’s surface moves with a period of about seven years.

This is the combined result of two effects.

The one we’re interested today is called the Chandler Wobble, which has a period of 433 days and was discovered by American astronomer Seth Carlo Chandler in 1891.

The Chandler Wobble is reasonably well understood.

Any spinning sphere that it is not entirely spherical should wobble in this way.

However, on Earth, the wobble varies in amplitude from decade to decade, a motion that is thought to be the result of the changes in pressure at the bottom of the oceans caused by fluctuations in salinity, temperature, and ocean circulation.

But there is also something mysterious about the Chandler Wobble.

In 1920, it underwent a sudden phase change of 180 degrees.

Nobody knows why.

Now a new analysis of data on Earth’s rotation going back 160 years indicates that this event was not unique.

Zinovy Malkin and Natalia Miller at the Russian Academy of Sciences Central Astronomical Observatory in Pulkovo say the phase has changed by small amounts on many occasions during this time.

But the big news is that the wobble underwent 180-degree changes in phase on two other occasions: once in 1850 and the other in 2005.

So why should the Chandler Wobble undergo these changes in phase?

An interesting puzzle for anybody with a few brain cycles to spare.

Ref: arxiv.org/abs/0908.3732: Chandler Wobble: Two More Large Phase Jumps Revealed

https://www.technologyreview.com/s/4150 ... y-in-2005/

[thelivyjr]

NASA

A Year in the Life of Carbon Dioxide

September 6, 2014 - September 6, 2015

Launched in 2014, the Orbiting Carbon Observatory-2 (OCO-2) has been collecting NASA’s first detailed, global measurements of carbon dioxide in the atmosphere.

The OCO-2 team recently released its first full year of data, which is critical to analyzing and understanding Earth’s carbon cycle.

The animated map above shows global average carbon dioxide concentrations as measured by OCO-2 from September 6, 2014, to September 6, 2015.

The satellite measures carbon dioxide from the top of Earth’s atmosphere to its surface.

Higher concentrations appear dark orange, while lower concentrations appear yellow.

The scale is relatively narrow, from 390 to 405 parts per million, the high and low measurements by OCO-2 in its first year.

Since the beginning of the industrial age, the global concentration of CO2 has increased from roughly an average of 280 parts per million to an average of 400 parts per million.

One recognizable pattern over the year is the annual uptake and release of carbon as each hemisphere passes through the seasons.

In the winter, carbon dioxide levels are at their peak in the northern hemisphere, when there is little plant or phytoplankton growth to offset emissions from human activities and natural sources.

At the same time, CO2 concentrations drop in the southern hemisphere, which is bathed in summer sunlight and heat.

The pattern reverses as the hemispheres change seasons.

According to the new measurements, atmospheric CO2 changes by 8 to 12 parts per million (2 to 3 percent) from winter through the “spring drawdown” in the northern hemisphere.

Over the course of a year, it is also clear that CO2 levels are generally higher over the northern hemisphere — where there are more people and more emissions — than in the southern hemisphere.

Both phenomena are well known to scientists, but OCO-2 now lets us see those patterns more clearly.

Scientists expect that more patterns will emerge on finer scales as the OCO-2 data set grows with time.

Though atmospheric carbon has been measured from stations on the ground — most famously at Mauna Loa in Hawaii — the value of OCO-2 is that it makes consistent measurements with the same instrument over all land and sea surfaces.

This was previously done, though at lower resolution and less frequency, by the Japanese GOSAT satellite.

NASA’s Atmospheric Infrared Sounder on the Aqua satellite also senses carbon dioxide, though higher in the atmosphere.

OCO-2 is NASA’s first spacecraft dedicated to studying the manmade and natural sources and sinks of carbon dioxide from the top of the atmosphere to the surface.

It uses high-resolution spectrometers that measure the intensity of sunlight at different wavelengths after it has passed down through the atmosphere, reflected off the land surface, and passed back up through the atmosphere.

Every day, OCO-2 orbits Earth 14.5 times and returns about a million measurements.

After eliminating data contaminated by clouds, aerosols, and steep terrain, between 10 to 13 percent of the measurements are of sufficient quality to derive accurate estimates of average carbon dioxide concentrations.

That's at least 100 times more carbon dioxide measurements than from all other sources combined.

“The new, exciting thing from my perspective is that we have more than 100,000 measurements each day of carbon dioxide in the atmosphere,” said Annmarie Eldering, OCO-2 deputy project scientist, based at NASA’s Jet Propulsion Laboratory.

“Armed with this pile of data, we can start to investigate more fully this question of sources and sinks and how different parts of the world contribute to these processes.”

Carbon naturally cycles through earthly environments.

Ocean water naturally absorbs carbon dioxide from the atmosphere, and floating, microscopic phytoplankton soak it up as well.

Trees, crops, and other plants on land take up carbon dioxide and turn it into the building blocks of roots, stems, branches, and leaves.

Some of that carbon stays in the soil as vegetation dies and gets buried, and some is released back into the atmosphere through plant respiration.

Both carbon dioxide and methane also are released through the decomposition of vegetation, land clearing, and fire.

Over many millennia, the pace of carbon cycling is even influenced by volcanic emissions and the weathering of rocks.

For most of human history, this rhythmic exchange of carbon has been more-or-less steady.

But the cycle has been thrown off in the past few centuries as ever-growing human populations have burned fossil fuels, cleared forests, and tilled soils for agriculture.

Today, about half of the carbon dioxide released by human activities stays in the atmosphere, warming and altering Earth’s climate.

The other half is removed from the air by the plants, plankton, and oceans.

“The huge question is: in the future, as the carbon dioxide builds up, will the land and the ocean continue to take up that 50 percent?” said Eldering.

“Do they get saturated or full, and they quit at some point, or do they always just take up more and more and more?”

NASA Earth Observatory maps by Joshua Stevens, using data from the OCO-2 science team at NASA-JPL and Caltech. Caption by Mike Carlowicz, based on reporting by Alan Buis (JPL) and Kate Ramsayer and Carol Rasmussen (NASA Earth Science News Team).

https://earthobservatory.nasa.gov/image ... on-dioxide

[thelivyjr]

Lysocline

From Wikipedia, the free encyclopedia

The lysocline is the depth in the ocean dependent upon the calcite compensation depth (CCD), usually around 3.5 km, below which the rate of dissolution of calcite increases dramatically because of a pressure effect.

While the lyscoline is the upper bound of this transition zone of calcite saturation, the CCD is the lower bound of this zone.

CaCO₃ content in sediment varies with different depths of the ocean, spanned by levels of separation known as the transition zone.

In the mid-depth area of the ocean, sediments are rich in CaCO₃, content values reaching 85-95%.

This area is then spanned hundred meters by the transition zone, ending in the abyssal depths with 0% concentration.

The lysocline is the upper bound of the transition zone, where amounts of CaCO₃ content begins to noticeably drop from the mid-depth 85-95% sediment.

The CaCO₃ content drops to 10% concentration at the lower bound, known as the calcite compensation depth.

Shallow marine waters are generally supersaturated in calcite, CaCO₃, because as marine organisms (which often have shells made of calcite or its polymorph, aragonite) die, they tend to fall downwards without dissolving.

As depth and pressure increases within the water column, calcite solubility increases, causing supersaturated water above the saturation depth, allowing for preservation and burial of CaCO₃ on the seafloor.

However, this created undersaturated seawater below the saturation depth, preventing CaCO₃ burial on the sea floor as the shells start to dissolve.

The equation Ω = Ca2+ + CO₃2-/K'sp expresses the CaCO₃ saturation state of seawater.

The calcite saturation horizon is where Ω =1; dissolution proceeds slowly below this depth.

The lysocline is the depth that this dissolution impacts is again notable, also known as the inflection point with sedimentary CaCO₃ versus various water depths.

Calcite Compensation Depth

The calcite compensation depth (CCD) occurs at the depth that the rate of calcite to the sediments is balanced with the dissolution flux, the depth at which the CaCO₃ content are values 2-10%.

Hence, the lysocline and CCD are not equivalent.

The lysocline and compensation depth occur at greater depths in the Atlantic (5000–6000 m) than in the Pacific (4000-5000 m), and at greater depths in equatorial regions than in polar regions.

The depth of the CCD varies as a function of the chemical composition of the seawater and its temperature.

Specifically, it is the deep waters that are undersaturated with calcium carbonate primarily because its solubility increases strongly with increasing pressure and salinity and decreasing temperature.

As the atmospheric concentration of carbon dioxide continues to increase, the CCD can be expected to decrease in depth, as the ocean's acidity rises.

https://en.wikipedia.org/wiki/Lysocline

[thelivyjr]

LAMONT-DOHERTY EARTH OBSERVATORY

THE EARTH INSTITUTE AT COLUMBIA UNIVERSITY

The Gulf Stream-European climate myth

Richard Seager, Lamont-Doherty Earth Observatory of Columbia University

Richard Seager's presentation to the New York Academy of Sciences: The Gulf Stream, European Climate and Abrupt Climate Change

A few times a year the British media of all stripes goes into a tizzy of panic when one climate scientist or another states that there is a possibility that the North Atlantic ocean circulation, of which the Gulf Stream is a major part, will slow down in coming years or even stop.

Whether the scientists' statements are measured or inflammatory the media invariably warns that this will plunge Britain and Europe into a new ice age, pictures of the icy shores of Labrador are shown, created film of English Channel ferries making their way through sea ice are broadcast...

And so the circus continues year after year.

Here is one example.

The Gulf Stream-European climate myth

The panic is based on a long held belief of the British, other Europeans, Americans and, indeed, much of the world's population that the northward heat transport by the Gulf Stream is the reason why western Europe enjoys a mild climate, much milder than, say, that of eastern North America.

This idea was actually originated by an American military man, Matthew Fontaine Maury, in the mid nineteenth century and has stuck since despite the absence of proof.

We now know this is a myth, the climatological equivalent of an urban legend.

In a detailed study published in the Quarterly Journal of the Royal Meteorological Society in 2002, we demonstrated the limited role that ocean heat transport plays in determining regional climates around the Atlantic Ocean.

Popular versions of this story can be found here, here and, in French, here.

The determinants of North Atlantic regional climates

We showed that there are three processes that need to be evaluated:

1. The ocean absorbs heat in summer and releases it in winter.

Regions that are downwind of oceans in winter will have mild climates.

This process does not require ocean currents or ocean heat transport.

2. The atmosphere moves heat poleward and warm climates where the heat converges.

In additions, the waviness in the atmospheric flow creates warm climates where the air flows poleward and cold climates where it flows equatorward.

3. The ocean moves heat poleward and will warm climates where it releases heat and the atmosphere picks it up and moves it onto land.

Using observations and climate models we found that, at the latitudes of Europe, the atmospheric heat transport exceeds that of the ocean by several fold.

In winter it may even by an order of magnitude greater.

Thus it is the atmosphere, not the ocean, that does the lion's share of the work ameliorating winter climates in the extratropics.

We also found that the seasonal absorption and release of heat by the ocean has a much larger impact on regional climates than does the movement of heat by ocean currents.

Seasonal storage and release accounts for half the winter temperature difference across the North Atlantic Ocean.

But the 500 pound gorilla in how regional climates are determined around the Atlantic turned out to be the Rocky Mountains.

Because of the need to conserve angular momentum, as air flows from the west across the mountains it is forced to first turn south and then to turn north further downstream.

As such the mountains force cold air south into eastern North America and warm air north into western Europe.

This waviness in the flow is responsible for the other half of the temperature difference across the North Atlantic Ocean.

Hence:

1. Fifty percent of the winter temperature difference across the North Atlantic is caused by the eastward atmospheric transport of heat released by the ocean that was absorbed and stored in the summer.

2. Fifty percent is caused by the stationary waves of the atmospheric flow.

3. The ocean heat transport contributes a small warming across the basin.

The seasonal ocean heat storage and pattern of atmospheric heat transport add up to make winters in western Europe 15 to 20 degrees C warmer than those in eastern North America.

A very similar process occurs across the Pacific Ocean.

The ocean heat transport warms the North Atlantic Ocean and the land on both sides by a modest few degrees C.

The only place where the ocean heat transport fundamentally alters climate is along the coast of northern Norway which would be sea ice-covered were it not for the warm northward flowing Norwegian Current.

The Gulf Stream and future climate change

A slowdown of the Gulf Stream and ocean circulation in the future, induced by freshening of the waters caused by anthropogenic climate change (via melting glaciers and increased water vapor transport into high latitudes) or simply by warming, would thus introduce a modest cooling tendency.

This would leave the temperature contrast across the Atlantic unchanged and not plunge Europe back into the ice age or anything like it.

In fact the cooling tendency would probably be overwhelmed by the direct radiatively-driven warming by rising greenhouse gases.

North Atlantic Ocean circulation and abrupt climate change

The conflation of the Gulf Stream, ocean heat transport and Europe's climate has led to changes in ocean circulation being the reigning theory of the cause of glacial era abrupt climate change.

These abrupt changes - the Dansgaard-Oeschger events of the last ice age and the Younger Dryas cold reversal of the last deglaciation - are well recorded in the Greenland ice core and Europe and involved changes in winter temperature of as much as thirty degrees C!

For the Younger Dryas it has been proposed that the sudden release of glacial meltwater from ice dammed Lake Agassiz freshened the North Atlantic and shut down the overturning circulation causing dramatic regional coooling.

Only through an inflated view of the impact of ocean circulation could it be thought that the enormous glacial era abrupt changes were caused by changes in ocean circulation.

Instead, as we have argued, changes in atmospheric circulation regimes had to be the driver, see (Seager and Battisti,2007).

Determining how this could happen has become more of a priority now that the geological evidence for the Lake Agassiz flood has not been found, see (Broecker,2006).

Moving beyond the myth

It is long time that the Gulf Stream-European climate myth was resigned to the graveyard of defunct misconceptions along with the Earth being flat and the sun going around the Earth.

In its place we need serious assessments of how changes in ocean circulation will impact climate change and a new look at the problem of abrupt climate change that gives the tropical climate system and the atmosphere their due as the primary drivers of regional climates around the world.

Publications

• Seager, R., D. S. Battisti, J. Yin, N. Gordon, N. H. Naik, A. C. Clement and M. A. Cane, 2002: Is the Gulf Stream responsible for Europe's mild winters? Quarterly Journal of the Royal Meteorological Society, 128(586): 2563-2586. PDF

• Seager, R. and D. S. Battisti, 2007: Challenges to our understanding of the general circulation: abrupt climate change. In: T. Schneider and A.S. Sobel (Editors), The Global Circulation of the Atmosphere: Phenomena, Theory, Challenges. Princeton University Press, pp. 331-371. PDF.

• Seager, R., 2006: The source of Europe's mild climate. American Scientist, 94(4): 334-341. PDF.

• Seager, R., 2008: Setting the record straight on Europe's mild winters. The Plantsman, Royal Horticultural Society,7, Part 1 March, p.22-27. PDF.

• Seager, R., 2003: Gulf Stream la fin d'un mythe. La Recherche(361): 40-46.PDF

http://ocp.ldeo.columbia.edu/res/div/ocp/gs/

[thelivyjr]

PHYS.ORG

The Gulf Stream is slowing down. That could mean rising seas and a hotter Florida

by David Fleshler

August 9, 2019

The Gulf Stream, the warm current that brings the east coast of Florida the mixed blessings of abundant swordfish, mild winters and stronger hurricanes, may be weakening because of climate change.

Visible from the air as a ribbon of cobalt blue water a few miles off the coast, the Gulf Stream forms part of a clockwise system of currents that transports warm water from the tropics up the east coast and across the Atlantic to northwestern Europe.

In the frigid climate near Greenland, the water cools, sinks and flows south again, rolling through the deep ocean toward the tropics.

This marine circulatory system has reached its weakest point in 1,600 years, recent studies show, having lost about 15% of its strength since the mid-20th century.

Scientists disagree on whether climate change or natural cycles account for the slowdown.

But a consensus has emerged that climate change will lead to a slower Gulf Stream system in the future, as melting ice sheets in Greenland disrupt the system with discharges of cold fresh water.

A weaker Gulf Stream would mean higher sea levels for Florida's east coast.

It could lead to colder winters in northern Europe (one reason many scientists prefer the term climate change to global warming).

And it could mean that a lot of the heat that would have gone to Europe would stay along the U.S. east coast and in Florida.

"If you slow down the sinking of water in the North Atlantic, that means you have a pileup of waters along the eastern seaboard of the United States and the Gulf of Mexico," said Brenda Ekwurzel, director of climate science for the Union of Concerned Scientists, an environmental group.

"That means that you have increased regional sea level rise just from that ocean circulation change."

"So that's not good for New York City, Norfolk or along Florida."

"Your cooling mechanism to get that water to the north is slowing down," she said.

"This slowing down of your natural air conditioning, by getting that hot water from the Gulf Stream flowing northward, means that you have that hotter water sticking around and not getting out of your region as fast."

It's unclear the extent to which any weakening has reached the system's southern leg off Florida, also known as the Florida current.

That current is driven partly by winds and partly by the pull from the sinking of cold water in the north.

While less visible than beaches and sunshine, the current plays a powerful role in establishing Florida's identity.

"It's one of the things that makes fishing so good here, the ability of the Gulf Stream to bring in migratory fish," said R.J. Boyle, a well-known swordfisherman who runs a Lighthouse Point fishing store.

"It's a funnel."

"We benefit because the Gulf Stream is so close to land."

"We catch swordfish, mahi-mahi, blue marlin and sailfish."

"The reason you catch all these fish in one area is because the Gulf Stream is here."

The Gulf Stream helps keep summers from getting too hot and winters from getting too cold.

Its warm water provides a ready supply of fuel to hurricanes crossing its path.

The role of climate change in hurricanes is the subject of extensive scientific inquiry, with some research suggesting we may see fewer hurricanes, with the ones that do form tending to be stronger and rainier.

A weaker Gulf Stream system could weigh in as a factor that reduces the number of hurricanes because it would tend to produce cooler water along the storms' Atlantic path.

"If the overall overturning circulation in the Atlantic Ocean weakens, in general it would mean overall generally weaker Atlantic hurricane seasons just because you tend to have cooler water and higher pressure in the deep tropics," said Philip Klotzbach, research scientist for Colorado State University's Tropical Meteorology Project.

"So that would tend to reduce hurricane activity, all else being equal."

Counteracting the cooling influence on the Atlantic, in a warmer world, would be the tendency of oceans to be warmer in general.

A weaker Gulf Stream could lead to higher sea levels along the Florida coast.

Sea level worldwide is currently rising at a rate of about one inch every eight years, partly because of melting ice sheets and partly because water expands as it warms.

But for local sea level, an important role is played by currents.

"If the Gulf Stream strengthens, you can think of that sort of sweeping the water away from the coast more rapidly and that tends to suppress sea level," said Ben Kirtman, professor of Atmospheric Sciences at the University of Miami's Rosenstiel School of Marine and Atmospheric Science.

"So a strong Gulf Stream is a good thing."

"And if the Gulf Stream weakens, just the opposite happens."

"It's not sweeping away the water as much, and so sea level rises."

"If the Gulf Stream weakens, it will exacerbate sea level rise."

Research into the fate of the Gulf Stream system, known as the Atlantic meridional overturning circulation, illustrates a broad truth about climate science.

While there's a consensus that the climate is warming and that this is happening largely because of human activities, scientists disagree on the likely impacts.

No one knows how fast glaciers will melt or how much sea level will rise and how quickly this will happen.

There's intense research into the potential impact on the frequency and strength of hurricanes and into the possible impact on plants, wildlife and human health.

With the Gulf Stream, scientists attempting to determine the role of climate change have to separate out natural factors, such as multi-decade temperature cycles in the Atlantic Ocean, that have strengthened or weakened the system for thousands of years.

"Detecting the climate change signal on top of the natural variability has really been a challenge," Kirtman said.

"There are articles saying it's not weakening, articles saying it's weakening."

"There's a lot of debate about it."

"I think the scientific consensus is that the jury's still out."

A key piece of evidence for a possible weakening of the current is a strange patch of cold water — dubbed by scientists the "cold blob" — south of Greenland.

While other parts of the earth have warmed, this area has cooled, and many scientists have concluded that this reflects a decline in the quantity of warm water reaching the area from the Gulf Stream.

"We see a cooling southeast of Greenland, although everywhere else on the globe you see a warming," said Levke Caesar, a scientist at the Potsdam Institute for Climate Impact Research in Germany and co-author of a study that found the current to be 15% weaker.

"When the circulation slows down, we have less heat transport to that region."

Normally, the current is driven by the cooling of water as it travels to the northern part of the Atlantic.

As water cools, it becomes denser and sinks.

This pulls warm water from the south to replace it.

But with climate change, melting glaciers and Arctic sea ice are overwhelming the system with fresh water, which is less dense and therefore less heavy than salt water, so less water sinks and less warm water is drawn from the south, disrupting the entire system.

Another study, published last year in the journal Nature, found the system to have reached its weakest point in 1,600 years, although it says the loss of strength probably began from natural factors.

The Fourth National Climate Assessment, published last November by a group of federal agencies, says there's insufficient data to conclude that the system has lost strength but says weakening over the next few decades is "very likely."

Whatever the causes, the possibility of a slowdown has caused concern on both sides of the Atlantic.

We don't think of Ireland, Great Britain and Germany as particularly warm countries, but they would be a lot colder without the Gulf Stream.

Ireland, for example, stands as far north as polar bear habitat in Canada.

But thanks partly to the Gulf Stream, water warmed by sunshine at the Equator flows up to Europe and moderates its temperatures.

"Gulf Stream slowing down is bad news for Ireland," reads a headline from The Irish Times.

Unlike other climate change phenomena, such as sea level rise, the collapse of the current could happen suddenly if it reaches a tipping point.

Scientists think that has taken place in the distant past.

"It's also possible that this will happen in the future, but it's really difficult to say when," said Caesar, of the Potsdam Institute.

"I think it's very likely that it won't happen in the next few decades."

"There are a few climate models that say it could happen."

https://phys.org/news/2019-08-gulf-stre ... orida.html

[thelivyjr]

NASA Earth Research Findings

NASA Finds Virginia Metro Area Is Sinking Unevenly

Nov. 27, 2017

A new NASA-led study shows that land in the Hampton Roads, Virginia, metropolitan area is sinking at highly uneven rates, with a few trouble spots subsiding 7 to 10 times faster than the area average.

Whereas earlier estimates had suggested the area is subsiding evenly, the new study found that major differences in subsidence rates occur only a few miles apart.

Hampton Roads has one of the highest rates of relative sea level rise -- the combined effects of sinking land and rising seas -- along the U.S. East Coast, about an inch (23 millimeters) every five years.

It has experienced a steady and dramatic increase in high-tide flooding over the last 90 years.

Accurate, local subsidence maps are necessary for the area to prepare for increasing flood risks in the future.

The region comprises seven Virginia cities, including Norfolk and Virginia Beach, as well as Naval Station Norfolk, the country’s largest naval base.

The new study, published in the journal Scientific Reports, found that much-higher-than-average subsidence is occurring at Craney Island, a depository for material dredged from shipping channels, and at the Norfolk Naval Shipyard, where the subsidence was most likely related to local construction during the study period.

In other areas with similarly high subsidence rates, the causes of the sinking are not known.

Researchers from NASA's Jet Propulsion Laboratory in Pasadena, California, and Old Dominion University (ODU) in Norfolk found the variations in subsidence by analyzing synthetic aperture radar (SAR) images acquired between 2007 and 2011 by the Japan Aerospace Exploration Agency's ALOS-1 satellite.

Processing the data with state-of-the-art image processing techniques, the researchers were able to document how the land surface had changed from the time of the first ALOS-1 image to 2011.

To tie in that relative data set with existing, lower-resolution maps of earlier subsidence, as well as to put the results into a framework already familiar to decision-makers, the researchers developed a new strategy to integrate the processed SAR measurements with Global Positioning System (GPS) observations.

The result was the first high-resolution estimates of vertical land motion in Hampton Roads.

The new estimates have a spatial resolution of about 100 feet (30 meters), whereas earlier estimates were based on data from GPS stations located 10 to 15 miles apart (about 20 kilometers).

The production of the new maps was a pilot project between JPL and ODU to assess the feasibility of using space-borne SAR data to map subsidence in Hampton Roads, according to lead author David Bekaert of JPL.

He noted that the techniques developed to make these maps integrating SAR and GPS measurements could be used to map subsidence at other locations.

The ALOS-1 data set used in this study is relatively small, with the satellite acquiring an image of the area only once every 46 days at best.

Bekaert and coauthors look forward to using data from the future NASA-Indian Space Research Organizaton Synthetic Aperture Radar (NISAR) mission, scheduled to launch in 2021, and from the European Space Agency's Sentinel-1 constellation, which currently acquires a new image of the Hampton Roads area every 12 days.

NISAR will also acquire an image every 12 days, but because of its longer operating wavelength and higher resolution, it is well placed to extend subsidence mapping into more challenging rural areas and wetlands.

"Continuing, regularly acquired SAR data will allow us to reduce the uncertainty in our subsidence rate estimates, which is important for decision-making," Bekaert said.

Coauthor Ben Hamlington (ODU) noted, "Information regarding subsidence should be incorporated into land use decisions and taken into consideration for future planning."

He has presented preliminary findings from this study to several planning and emergency management committees in Hampton Roads.

Hamlington said, "We had a need for high-resolution images of subsidence, but we didn't have the expertise and technology to do the analysis ourselves here at ODU."

"Collaborating with JPL helped us build capacity for the future, and also get immediate results."

NASA's associate program manager for disasters, John Murray of NASA's Langley Research Center in Hampton, connected the ODU and JPL scientists.

The study was funded by NASA's Earth Science Disasters Program and the Commonwealth Center for Recurrent Flooding Resiliency, jointly operated by ODU and the College of William & Mary, Norfolk.

The paper in Scientific Reports is titled "Spaceborne Synthetic Aperture Radar Survey of Subsidence in Hampton Roads, Virginia (USA)."

Alan Buis
Jet Propulsion Laboratory, Pasadena, California
818-354-0474
Alan.Buis@jpl.nasa.gov

Jon Cawley
Old Dominion University, Norfolk, Virginia
757-683-6479
jcawley@odu.edu

Written by Carol Rasmussen
NASA's Earth Science News Team

Last Updated: Nov. 29, 2017

Editor: Tony Greicius

https://www.nasa.gov/feature/jpl/nasa-f ... g-unevenly

[thelivyjr]

News from the Earth Institute - Columbia University

"Could Climate Change Shut Down the Gulf Stream?"

by Renee Cho

June 6, 2017

The 2004 disaster movie “The Day After Tomorrow” depicted the cataclysmic effects — superstorms, tornadoes and deep freezes — resulting from the impacts of climate change.

In the movie, global warming had accelerated the melting of polar ice, which disrupted circulation in the North Atlantic Ocean, triggering violent changes in the weather.

Scientists pooh-poohed the dire scenarios in the movie, but affirmed that climate change could indeed affect ocean circulation — could it shut down the Gulf Stream?

The many ocean currents and wind systems that move heat from the equator northwards towards the poles then transport the cold water back towards the equator make up the thermohaline circulation.

(Thermo refers to temperature while haline denotes salt content; both factors determine the density of ocean waters.)

It is also called the Great Ocean Conveyor, a term coined in 1987 by Wallace Broecker, Newberry Professor of Geology in the Department of Earth and Environmental Sciences at Columbia University and a scientist at Lamont-Doherty Earth Observatory.

Broecker theorized that changes in the thermohaline circulation triggered dramatic changes in the North Atlantic during the last ice age.

In the high latitudes, the cold water on the surface of the ocean gets saltier as some water evaporates and/or salt is ejected in the forming of sea ice.

Because saltier colder water is denser and thus heavier, it drops deep into the ocean and moves along the depths until it can rise to the surface near the equator, usually in the Pacific and Indian Oceans.

Heat from the sun then warms the cold water at the surface, and evaporation leaves the water saltier.

The warm salty water is then carried northwards; it joins the Gulf Stream, a large powerful ocean current that is also driven by winds.

The warm salty water travels up the U.S. east coast, then crosses into the North Atlantic region where it releases heat and warms Western Europe.

Once the water releases its heat and reaches the North Atlantic, it becomes very cold and dense again, and sinks to the deep ocean.

The cycle continues.

The thermohaline circulation plays a key role in determining the climate of different regions of the earth.

The Atlantic Meridional Overturning Circulation, part of the thermohaline circulation which includes the Gulf Stream, is the ocean circulation system that carries heat north from the tropics and Southern Hemisphere until it loses it in the northern North Atlantic, Nordic and Labrador Seas, which leads to the deep sinking of the colder waters.

Because the thermohaline circulation is mainly driven by differences in the water’s density, it depends upon the cold dense waters that sink into the deep oceans.

Global warming can affect this by warming surface waters and melting ice that adds fresh water to the circulation, making the waters less saline; this freshening of the water can prevent the cold waters from sinking and thus alter ocean currents.

As the planet warms, more and more fresh water is entering the system.

In 2016, the extent of Greenland’s melting sea ice set a new record low.

That May, the Arctic lost about 23,600 square miles of ice daily, compared to the long-term average loss of 18,000 square miles per day.

A study by Marco Tedesco, a research professor at Lamont-Doherty specializing in Greenland, and colleagues suggested that a reduction in the temperature difference between the polar and temperate regions (the Arctic is warming twice as fast as the rest of the planet) pulled the jet stream air currents northwards.

The warm moist air it carried hovered over Greenland, causing the record melting.

So far this year, Tedesco said, “The melting in Greenland is within the mean, but it’s still above the average of what was happening 20 years ago…"

"The snow melt from Siberia has also been melting sooner, there’s been more fresh water from Greenland, there’s more fresh water from sea ice in the Arctic Ocean and more fresh water from North Canada which has been melting at an increasing rate."

"All these factors are pointing in the direction of increasing the freshwater discharge in the North Atlantic section of the Arctic."

"It’s very likely going to have an impact.”

In addition to warming temperatures accelerating Greenland’s melting, the snow and ice are being darkened by black carbon, (reducing their reflectivity and warming the snow), and wind-blown algae and bacteria that are growing in holes in the ice.

“More biological activity implies darker surfaces which in turn implies more melting,” said Tedesco.

“But I think there is still not enough knowledge to properly project [what the impacts could be]…"

"We know there is an impact and it’s important to quantify that impact because we need to know what the processes that we need to consider are to do proper projections.”

A 2015 study hypothesized that fresh water, which increased in the northern Atlantic by more than 4,500 cubic miles (19,000 km3) between 1961 and 1995, weakened the deep water formation of the Atlantic Meridional Overturning Circulation, particularly after 1975.

The circulation has slowed between 15 and 20 percent in the 20th century, an anomaly unprecedented over the last millennium, which suggests it is not due to natural variability.

The scientists hypothesized that this could explain why, in 2014, a specific patch in the middle of the North Atlantic was the coldest on record since 1880 while global temperatures everywhere else were increasing.

The study suggested that the unusual cooling of this region could be due to a weakening of the global conveyor that is already occurring.

(It seems to have made a partial recovery since 1990.)

Michael Mann, Distinguished Professor of Atmospheric Science at Penn State University, one of the study’s authors, noted that if the Atlantic Meridional Overturning Circulation were to totally collapse over the next few decades, it would change ocean circulation patterns, influence the food chain, and negatively impact fish populations.

We would not return to very cold conditions, however, because the oceans have taken up so much heat.

Another 2015 study that modeled a hypothetical slowdown or collapse of the Atlantic Meridional Overturning Circulation concluded that a collapse could result in widespread cooling throughout the North Atlantic and Europe (though this would be somewhat mitigated by global warming), increased sea ice in the North Atlantic, changes in tropical precipitation patterns, stronger North Atlantic storms, reduced precipitation and river flow as well as reduced crop productivity in Europe.

These effects would impact many regions around the globe.

Sea levels would be affected as well.

Currently sea levels are lower on the U.S. east coast because waters east of the Gulf Stream, closer to Europe, are warmer and expand, so sea levels there are higher.

If the Gulf Stream is weakened, the temperature differential between the two sides is reduced, so sea levels will rise on the west of the Gulf Stream along the U.S. east coast and the North Atlantic.

In fact, sea levels along the coast and the Gulf of Mexico are rising faster than in any other part of the U.S, and some data suggests that it is because the Gulf Stream has already begun to slow down.

Other research attributed a jump in sea level rise from New York to Newfoundland from 2009 to 2010 to the Atlantic Meridional Overturning Circulation slowing down 30 percent in the same period, as well as unusual wind currents that pushed ocean waters towards the coast.

Not all scientists agree that the Atlantic Meridional Overturning Circulation is slowing or that if it is, the phenomenon is caused by human induced global warming.

A 2016 study suggested that while a great deal of fresh water has been discharged from Greenland, it’s difficult to track what happens to it because of eddies and currents.

This research concluded that most of Greenland’s meltwater moves southward, and what remains of the fresh water is not enough to affect the Atlantic Meridional Overturning Circulation.

The scientists did acknowledge, however, that the ongoing rapid melting of Greenland and increases of fresh water could eventually affect it.

The bottom line is that the thermohaline circulation is a very complex system and scientists do not yet understand all the variables involved in how it functions.

There is an ongoing debate about why the Atlantic Meridional Overturning Circulation has weakened and how much is due to the effects of human activity on the climate.

In the Earth’s past, scientists have seen evidence of large inputs of fresh water into the North Atlantic from melting glaciers and ice caps as well as changes in the thermohaline circulation during transitions in and out of glacial periods.

Global warming could potentially cause a thermohaline circulation shutdown and subsequent regional cooling, but because Earth will continue to warm as a result of greenhouse gas emissions, it would not produce another Ice Age.

If the thermohaline circulation shut down, cooling would likely occur only in regions that are currently warmed by the ocean conveyor.

And even if the thermohaline circulation did shut down, winds would still likely drive the Gulf Stream; however, there would be less warm water from the tropics and the Gulf Stream could become cooler and not reach as far north.

The 5th assessment report of the Intergovernmental Panel on Climate Change says, “…the Atlantic Meridional Overturning Circulation is generally projected to weaken over the next century in response to increase in atmospheric greenhouse gas emissions…."

"Overall, it is likely that there will be some decline in the AMOC by 2050, but decades during which the AMOC increases are also to be expected.”

According to Broecker, although reorganizations of ocean circulation are at the core of what happened in the past, we cannot say what the likelihood is that warming due to greenhouse gases will trigger yet another large and abrupt change.

But if it were to occur, the consequences would be far less severe since, in the past, large existing expanses of sea ice were significant players in cooling the planet.

“A conveyor shutdown is not likely,” said Broecker.

“But if it happened, it would be ten times less dramatic and important than what happened during the glacial period when it caused a 10˚C temperature change.”

“We are monitoring the strength of deep water going south,” he said.

“And we are finding large seasonal changes and interannual changes…"

"It’s a complicated system and we can’t make any predictions.”

“The important thing is to understand better what is happening, by when it’s happening and what the potential implications will be,” said Tedesco.

“Our priority is to better estimate the behavior of the Arctic and its connections to the temperate part of the planet in the short and long term…"

"The question is not if things are going to change, the thing is how fast and when are they going to change, and what are the changes we’re going to see."

"There are changes at the local scale that are occurring on a much shorter time frame, and changes in the long-term that could include the shutdown of the ocean circulation."

"We need to understand the processes to properly build the models [to make projections].”

Lamont-Doherty’s Arctic Switchyard Project explores the circulation, variability, and driving mechanisms of the fresh water arriving in the Arctic Ocean, north of the eastern Canadian Archipelago and Greenland.

https://blogs.ei.columbia.edu/2017/06/0 ... lf-stream/

[thelivyjr]

NOAA

"Climate Change: Global Temperature"

Author: Rebecca Lindsey and LuAnn Dahlman

January 16, 2020

Given the size and tremendous heat capacity of the global oceans, it takes a massive amount of heat energy to raise Earth’s average yearly surface temperature even a small amount.

The 2-degree increase in global average surface temperature that has occurred since the pre-industrial era (1880-1900) might seem small, but it means a significant increase in accumulated heat.

That extra heat is driving regional and seasonal temperature extremes, reducing snow cover and sea ice, intensifying heavy rainfall, and changing habitat ranges for plants and animals—expanding some and shrinking others.

Conditions in 2019

According to the 2019 Global Climate Report from NOAA National Centers for Environmental Information, 2019 began with a weak-to-moderate El Niño event underway in the tropical Pacific Ocean.

Temperatures were warmer than average across most global land and ocean areas during most of the year.

Record high annual temperatures over land surfaces were measured across parts of central Europe, Asia, Australia, southern Africa, Madagascar, New Zealand, North America, and eastern South America.

Record high sea surface temperatures were observed across parts of all oceans, including the North and South Atlantic Ocean, the western Indian Ocean, and areas of northern, central and southwestern Pacific Ocean.

No land or ocean areas were record cold for the year, and the only substantial pocket of cooler-than-average land temperatures was in central North America.

Change over time

Though warming has not been uniform across the planet, the upward trend in the globally averaged temperature shows that more areas are warming than cooling.

According to the NOAA 2019 Global Climate Summary, the combined land and ocean temperature has increased at an average rate of 0.07°C (0.13°F) per decade since 1880; however, the average rate of increase since 1981 (0.18°C / 0.32°F) is more than twice as great.

The 10 warmest years on record have all occurred since 1998, and 9 of the 10 have occurred since 2005.

The year 1998 is the only year from the twentieth century still among the ten warmest years on record.

Looking back to 1988, a pattern emerges: except for 2011, as each new year is added to the historical record, it becomes one of the top 10 warmest on record at that time, but it is ultimately replaced as the “top ten” window shifts forward in time.

By 2020, models project that global surface temperature will be more than 0.5°C (0.9°F) warmer than the 1986-2005 average, regardless of which carbon dioxide emissions pathway the world follows.

This similarity in temperatures regardless of total emissions is a short-term phenomenon: it reflects the tremendous inertia of Earth's vast oceans.

The high heat capacity of water means that ocean temperature doesn't react instantly to the increased heat being trapped by greenhouse gases.

By 2030, however, the heating imbalance caused by greenhouse gases begins to overcome the oceans' thermal inertia, and projected temperature pathways begin to diverge, with unchecked carbon dioxide emissions likely leading to several additional degrees of warming by the end of the century.

About surface temperature

The concept of an average temperature for the entire globe may seem odd.

After all, at this very moment, the highest and lowest temperatures on Earth are likely more than 100°F (55°C) apart.

Temperatures vary from night to day and between seasonal extremes in the Northern and Southern Hemispheres.

This means that some parts of Earth are quite cold while other parts are downright hot.

To speak of the "average" temperature, then, may seem like nonsense.

However, the concept of a global average temperature is convenient for detecting and tracking changes in Earth's energy budget — how much sunlight Earth absorbs minus how much it radiates to space as heat — over time.

To calculate a global average temperature, scientists begin with temperature measurements taken at locations around the globe.

Because their goal is to track changes in temperature, measurements are converted from absolute temperature readings to temperature anomalies — the difference between the observed temperature and the long-term average temperature for each location and date.

Multiple independent research groups across the world perform their own analysis of the surface temperature data, and they all show a similar upward trend.

Across inaccessible areas that have few measurements, scientists use surrounding temperatures and other information to estimate the missing values.

Each value is then used to calculate a global temperature average.

This process provides a consistent, reliable method for monitoring changes in Earth's surface temperature over time.

References

Sánchez-Lugo, A., Berrisford, P., Morice, C., and Argüez, A. (2018). Temperature [in State of the Climate in 2018]. Bulletin of the American Meteorological Society, 99(8), S11–S12.

NOAA National Centers for Environmental Information, State of the Climate: Global Climate Report for Annual 2019, published online January 2020, retrieved on January 16, 2020 from https://www.ncdc.noaa.gov/sotc/global/201913.

IPCC, 2013: Summary for Policymakers. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group 1 to the 5th Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Interactive graph data

Annual global temperature anomalies for land and ocean combined, expressed as departures from the 1901-2000 average. National Climatic Data Center.

Highlights:

• In 2019, the average temperature across global land and ocean surfaces was 1.71°F (0.95°C) above the twentieth-century average of 57.0°F (13.9°C), making it the second-warmest year on record.

• The global annual temperature has increased at an average rate of 0.07°C (0.13°F) per decade since 1880 and over twice that rate (+0.18°C / +0.32°F) since 1981.

• The five warmest years in the 1880–2019 record have all occurred since 2015, while nine of the 10 warmest years have occurred since 2005.

• From 1900 to 1980 a new temperature record was set on average every 13.5 years; since 1981, it has increased to every 3 years.

https://www.climate.gov/news-features/u ... emperature

[thelivyjr]

CLIMATE CENTRAL

Hot and Getting Hotter: Heat Islands Cooking U.S. Cities

Published: August 20th, 2014

Research Report by Climate Central

Cities are almost always hotter than the surrounding rural area but global warming takes that heat and makes it worse.

In the future, this combination of urbanization and climate change could raise urban temperatures to levels that threaten human health, strain energy resources, and compromise economic productivity.

Summers in the U.S. have been warming since 1970.

But on average across the country cities are even hotter, and have been getting hotter faster than adjacent rural areas.

With more than 80 percent of Americans living in cities, these urban heat islands — combined with rising temperatures caused by increasing heat-trapping greenhouse gas emissions — can have serious health effects for hundreds of millions of people during the hottest months of the year.

Heat is the No.1 weather-related killer in the U.S., and the hottest days, particularly days over 90°F, are associated with dangerous ozone pollution levels that can trigger asthma attacks, heart attacks, and other serious health impacts.

Our analysis of summer temperatures in 60 of the largest U.S. cities found that:

57 cities had measurable urban heat island effects over the past 10 years.

Single-day urban temperatures in some metro areas were as much as 27°F higher than the surrounding rural areas, and on average across all 60 cities, the maximum single-day temperature difference was 17.5°F.

Cities have many more searing hot days each year.

Since 2004, 12 cities averaged at least 20 more days a year above 90°F than nearby rural areas.

The 60 cities analyzed averaged at least 8 more days over 90°F each summer compared to adjacent rural areas.

More heat can increase ozone air pollution.

All 51 cities with adequate data showed a statistically significant correlation between higher daily summer temperatures and bad air quality (as measured by ground-level ozone concentrations).

Temperatures are being forced higher by increasing urbanization and manmade global warming, which could undermine the hard-won improvements in air quality and public health made over the past few decades.

In two thirds of the cities analyzed (41 of 60), urbanization and climate change appear to be combining to increase summer heat faster than climate change alone is raising regional temperatures.

In three quarters (45 of 60) of cities examined, urbanized areas are warming faster than adjacent rural locations.

The top 10 cities with the most intense summer urban heat islands (average daily urban-rural temperature differences) over the past 10 years are:

Las Vegas (7.3°F)
Albuquerque (5.9°F
Denver (4.9°F)
Portland (4.8°F)
Louisville (4.8°F)
Washington, D.C. (4.7°F)
Kansas City (4.6°F)
Columbus (4.4°F)
Minneapolis (4.3°F)
Seattle (4.1°F)

On average across all 60 cities, urban summer temperatures were 2.4°F hotter than rural temperatures.

Urban heat islands are even more intense at night.

Over the past 10 years, average summer overnight temperatures were more than 4°F hotter in cities than surrounding rural areas.

Several independent studies have shown that urban heat islands (in the U.S., and around the world) do not bias global warming measurements, ruling out the possibility that rising global temperatures have been caused by urbanization alone.

Research suggests that urban planning and design that incorporates more trees and parks, white roofs, and alternative materials for urban infrastructure can help reduce the effects of urban heat islands.

But rising greenhouse gas emissions are projected to drive average U.S summer temperatures even higher in the coming decades, exacerbating urban heat islands and their associated health risks.

Research report written by Alyson Kenward, Senior Scientist and Research Director for Climate Central; Dan Yawitz, Research Analyst and Multimedia Fellow; Todd Sanford, Climate Scientist; and Regina Wang, Research Fellow.

https://www.climatecentral.org/news/urb ... alth-17919