Archive for the ‘climate change – global warming’ Category

Global warming is affecting the world’s lakes

May 18, 2017

Lakes worldwide feel the heat from climate change, Warming waters are disrupting freshwater fishing and recreation, Science News ,BY ALEXANDRA WITZE  MAY 1, 2017 “……..When most people think of the physical effects of climate change, they picture melting glaciers, shrinking sea ice or flooded coastal towns (SN: 4/16/16, p. 22). But observations like those at Stannard Rock are vaulting lakes into the vanguard of climate science. Year after year, lakes reflect the long-term changes of their environment in their physics, chemistry and biology. “They’re sentinels,” says John Lenters, a limnologist at the University of Wisconsin–Madison.

Globally, observations show that many lakes are heating up — but not all in the same way or with the same ecological consequences. In eastern Africa, Lake Tanganyika is warming relatively slowly, but its fish populations are plummeting, leaving people with less to eat. In the U.S. Upper Midwest, quicker-warming lakes are experiencing shifts in the relative abundance of fish species that support a billion-dollar-plus recreational industry. And at high global latitudes, cold lakes normally covered by ice in the winter are seeing less ice year after year — a change that could affect all parts of the food web, from algae to freshwater seals.

Understanding such changes is crucial for humans to adapt to the changes that are likely to come, limnologists say. Indeed, some northern lakes will probably release more methane into the air as temperatures rise — exacerbating the climate shift that is already under way.

Lake layers

Lakes and ponds cover about 4 percent of the land surface not already covered by glaciers. That may sound like a small fraction, but lakes play a key role in several planetary processes. Lakes cycle carbon between the water’s surface and the atmosphere. They give off heat-trapping gases such as
carbon dioxide and methane, while simultaneously tucking away carbon in decaying layers of organic muck at lake bottoms. They bury nearly half as much carbon as the oceans do.

Yet the world’s more than 100 million lakes are often overlooked in climate simulations. That’s surprising, because lakes are far easier to measure than oceans. Because lakes are relatively small, scientists can go out in boats or set out buoys to survey temperature, salinity and other factors at different depths and in different seasons.

A landmark study published in 2015 aimed to synthesize these in-water measurements with satellite observations for 235 lakes worldwide. In theory, lake warming is a simple process: The hotter the air above a lake, the hotter the waters get. But the picture is far more complicated than that, the international team of researchers found.

Globally, observations show that many lakes are heating up — but not all in the same way or with the same ecological consequences. In eastern Africa, Lake Tanganyika is warming relatively slowly, but its fish populations are plummeting, leaving people with less to eat. In the U.S. Upper Midwest, quicker-warming lakes are experiencing shifts in the relative abundance of fish species that support a billion-dollar-plus recreational industry. And at high global latitudes, cold lakes normally covered by ice in the winter are seeing less ice year after year — a change that could affect all parts of the food web, from algae to freshwater seals.

Understanding such changes is crucial for humans to adapt to the changes that are likely to come, limnologists say. Indeed, some northern lakes will probably release more methane into the air as temperatures rise — exacerbating the climate shift that is already under way.

Lake layers

Lakes and ponds cover about 4 percent of the land surface not already covered by glaciers. That may sound like a small fraction, but lakes play a key role in several planetary processes. Lakes cycle carbon between the water’s surface and the atmosphere. They give off heat-trapping gases such as
carbon dioxide and methane, while simultaneously tucking away carbon in decaying layers of organic muck at lake bottoms. They bury nearly half as much carbon as the oceans do.

Yet the world’s more than 100 million lakes are often overlooked in climate simulations. That’s surprising, because lakes are far easier to measure than oceans. Because lakes are relatively small, scientists can go out in boats or set out buoys to survey temperature, salinity and other factors at different depths and in different seasons.

A landmark study published in 2015 aimed to synthesize these in-water measurements with satellite observations for 235 lakes worldwide. In theory, lake warming is a simple process: The hotter the air above a lake, the hotter the waters get. But the picture is far more complicated than that, the international team of researchers found.

On average, the 235 lakes in the study warmed at a rate of 0.34 degrees Celsius per decade between 1985 and 2009. Some warmed much faster, like Finland’s Lake Lappajärvi, which soared nearly 0.9 degrees each decade. A few even cooled, such as Blue Cypress Lake in Florida. Puzzlingly, there was no clear trend in which lakes warmed and which cooled. The most rapidly warming lakes were scattered across different latitudes and elevations.

Even some that were nearly side by side warmed at different rates from one another — Lake Superior, by far the largest of the Great Lakes, is warming much more rapidly, at a full degree per decade, than others in the chain, although Huron and Michigan are also warming fast.

“Even though lakes are experiencing the same weather, they are responding in different ways,” says Stephanie Hampton, an aquatic biologist at Washington State University in Pullman.

Such variability makes it hard to pin down what to expect in the future. But researchers are starting to explore factors such as lake depth and lake size (intuitively, it’s less teeth-chattering to swim in a small pond in early summer than a big lake).

Depth and size play into stratification, the process through which some lakes separate into layers of different temperatures. …….https://www.sciencenews.org/article/lakes-worldwide-feel-heat-climate-change?tgt=nr

The vanishing Arctic ice

May 18, 2017

The hard truth, however, is that the Arctic as it is known today is almost certainly gone. Efforts to mitigate global warming by cutting emissions remain essential. But the state of the Arctic shows that humans cannot simply undo climate change. They will have to adapt to it

The Arctic as it is known today is almost certainly gone On current trends, the Arctic will be ice-free in summer by 2040 http://www.economist.com/news/leaders/21721379-current-trends-arctic-will-be-ice-free-summer-2040-arctic-it-known-today?fsrc=scn/tw/te/bl/ed/climatechangethearcticasitisknowntodayisalmostcertainlygone Apr 29th 2017

THOSE who doubt the power of human beings to change Earth’s climate should look to the Arctic, and shiver. There is no need to pore over records of temperatures and atmospheric carbon-dioxide concentrations. The process is starkly visible in the shrinkage of the ice that covers the Arctic ocean. In the past 30 years, the minimum coverage of summer ice has fallen by half; its volume has fallen by three-quarters. On current trends, the Arctic ocean will be largely ice-free in summer by 2040.

Climate-change sceptics will shrug. Some may even celebrate: an ice-free Arctic ocean promises a shortcut for shipping between the Pacific coast of Asia and the Atlantic coasts of Europe and the Americas, and the possibility of prospecting for perhaps a fifth of the planet’s undiscovered supplies of oil and natural gas. Such reactions are profoundly misguided. Never mind that the low price of oil and gas means searching for them in the Arctic is no longer worthwhile. Or that the much-vaunted sea passages are likely to carry only a trickle of trade. The right response is fear. The Arctic is not merely a bellwether of matters climatic, but an actor in them (see Briefing).

The current period of global warming that Earth is undergoing is caused by certain gases in the atmosphere, notably carbon dioxide. These admit heat, in the form of sunlight, but block its radiation back into space, in the form of longer-wavelength infra-red. That traps heat in the air, the water and the land. More carbon dioxide equals more warming—a simple equation. Except it is not simple. A number of feedback loops complicate matters. Some dampen warming down; some speed it up. Two in the Arctic may speed it up quite a lot.

One is that seawater is much darker than ice. It absorbs heat rather than reflecting it back into space. That melts more ice, which leaves more seawater exposed, which melts more ice. And so on. This helps explain why the Arctic is warming faster than the rest of the planet. The deal on climate change made in Paris in 2015 is meant to stop Earth’s surface temperature rising by more than 2°C above pre-industrial levels. In the unlikely event that it is fully implemented, winter temperatures over the Arctic ocean will still warm by between 5° and 9°C compared with their 1986-2005 average.

The second feedback loop concerns not the water but the land. In the Arctic much of this is permafrost. That frozen soil locks up a lot of organic material. If the permafrost melts its organic contents can escape as a result of fire or decay, in the form of carbon dioxide or methane (which is a more potent greenhouse gas than CO2). This will speed up global warming directly—and the soot from the fires, when it settles on the ice, will darken it and thus speed its melting still more.

Dead habitat walking

 A warming Arctic could have malevolent effects. The world’s winds are driven in large part by the temperature difference between the poles and the tropics. If the Arctic heats faster than the tropics, this difference will decrease and wind speeds will slow—as they have done, in the northern hemisphere, by between 5 and 15% in the past 30 years. Less wind might sound desirable. It is not. One consequence is erratic behaviour of the northern jet stream, a circumpolar current, the oscillations of which sometimes bring cold air south and warm air north. More exaggerated oscillations would spell blizzards and heatwaves in unexpected places at unexpected times.

Ocean currents, too, may slow. The melting of Arctic ice dilutes salt water moving north from the tropics. That makes it less dense, and thus less inclined to sink for the return journey in the ocean depths. This slowing of circulation will tug at currents around the world, with effects on everything from the Indian monsoon to the pattern of El Niño in the Pacific ocean.

The scariest possibility of all is that something happens to the ice cap covering Greenland. This contains about 10% of the world’s fresh water. If bits of it melted, or just broke free to float in the water, sea levels could rise by a lot more than today’s projection of 74cm by the end of the century. At the moment, the risk of this happening is hard to assess because data are difficult to gather. But loss of ice from Greenland is accelerating.

What to do about all this is a different question. Even if the Paris agreement is stuck to scrupulously, the amount of carbon dioxide already in the atmosphere, together with that which will be added, looks bound eventually to make summer Arctic sea ice a thing of the past. Some talk of geoengineering—for example, spraying sulphates into the polar air to reflect sunlight back into space, or using salt to seed the creation of sunlight-blocking clouds. Such ideas would have unknown side-effects, but they are worth testing in pilot studies.

The hard truth, however, is that the Arctic as it is known today is almost certainly gone. Efforts to mitigate global warming by cutting emissions remain essential. But the state of the Arctic shows that humans cannot simply undo climate change. They will have to adapt to it.

Arctic warm water is now being pushed to the surface

May 18, 2017
Climate change is literally turning the Arctic ocean inside out, WP,  April 6 There’s something special — and very counterintuitive — about the Arctic Ocean.

Unlike in the Atlantic or Pacific, where the water gets colder as it gets deeper, the Arctic is upside-down. The water gets warmer as it gets deeper. The reason is that warm, salty Atlantic-originating water that flows into the Arctic from the south is more dense, and so it nestles beneath a colder, fresher surface layer that is often capped by floating sea ice. This state of “stratification” makes the Arctic Ocean unique, and it means that waters don’t simply grow colder as you travel farther north — they also become inverted.

But in a paper in Science released Thursday, a team of Arctic scientists say this fundamental trait is now changing across a major part of the Arctic, in conjunction with a changing climate.

“I first went to the Arctic in about 1969, and I’ve never seen anything like this,” said Eddy Carmack, a researcher with Fisheries and Oceans Canada and one of the study’s authors. “Back then we just assumed the Arctic is as it is and it will be that way forevermore. So what we’re seeing in the last decade or so is quite remarkable.”

In a large area that they term the eastern Eurasian basin — north of the Laptev and East Siberian seas, which in turn are north of Siberia — the researchers found that warm Atlantic water is increasingly pushing to the surface and melting floating sea ice. This mixing, they say, has not only contributed to thinner ice and more areas of open water that used to be ice covered, but it also is changing the state of Arctic waters in a process the study terms “Atlantification” — and these characteristics could soon spread across more of the Arctic ocean, changing it fundamentally.

The study was led by Igor Polyakov of the University of Alaska at Fairbanks, in collaboration with a team of 15 researchers from the United States, Canada, Russia, Poland, Germany and Norway.

To understand the work, it’s important to first note the extensive and rapid shrinkage of Arctic sea ice of late in an area to the north of Siberia. The area, known as the eastern Eurasian basin, is seeing thinner ice and more months of open water. Arctic sea ice is a linchpin of the Earth’s climate system………https://www.washingtonpost.com/news/energy-environment/wp/2017/04/06/scientists-say-the-unique-arctic-ocean-is-being-transformed-before-our-eyes/?utm_campaign=crowdfire&utm_content=crowdfire&utm_medium=social&utm_source=twitter&utm_term=.40ec22cba221#350509998-tw#1491570060364

Climate change physics

May 18, 2017

Elevator Pitches – Chapter 02 – Radiative Gases Radiative Gases

A Musical Basis for Scattering Heat https://www.skepticalscience.com/ccep02.html24 March 2017 by Rob Honeycutt – This is another excerpt from my book 28 Climate Change Elevator Pitches. I’ll be publishing one chapter here on SkS each month.The scientific basis for understanding climate goes back to the 1820’s when brilliant French mathematician Joseph Fourier first proposed the idea that our planet’s atmosphere had heat-trapping properties. Fourier was trying to calculate what should be the temperature of a planet at our distance from the sun. He derived a figure about 33°C (59°F) colder than the actual average temperature of the Earth. For his figures to be correct, he thought gases in our atmosphere must have “radiative properties” with the capacity to absorb and re-emit heat energy. When visible sunlight passes through our atmosphere it warms the surface of the Earth. The heat that is emitted upward we refer to as infrared radiation, or IR. Infrared radiation is just another wavelength of energy which is invisible to the human eye, but we can feel that energy as heat. It’s this heat energy that is scattered by radiative gases in the atmosphere.

In the 1850’s a British scientist, John Tyndall, devised an apparatus enabling him to measure the heat absorbing properties of various gases. Earth’s atmosphere is composed primarily of nitrogen (78%) and oxygen (21%). The remaining 1 percent of gases are known as “trace gases.” Tyndall discovered that the radiative properties of nitrogen and oxygen are insignificant and transparent to infrared radiation (heat). But, he further discovered that some trace gases do efficiently block heat.

But, how does this work? Why would one gas be transparent to heat and another gas block it?

The most common radiative gases in our atmosphere are water (H2O), carbon dioxide(CO2), and to a lesser extent, methane (CH4), so let’s look at how these molecules are constructed. The first two have a single core atom with two other atoms attached to it. With H2O, there is a central oxygen atom with two hydrogen atoms attached. With CO2, there is a central carbon atom and two oxygen atoms attached. You can picture these being something like soap bubbles joined together, but imagine if you can, that these soap bubbles have an electromagnetic field incorporated into them. This electromagnetic field gently locks the molecule into a specific configuration. That magnetic field also allows the atoms to wobble around a bit as the molecule is floating about in the atmosphere. Methane is somewhat similarly constructed as CO2, but with a central carbon atom surrounded on four sides by hydrogen atoms making it a far more potent radiative gas than the others.

Infrared radiation is a wavelength of light. In a way, it’s analogous to sound waves traveling through the air. If you tap an A note tuning fork on your knee and then hold it against the soundboard of a guitar the A-string of the guitar will vibrate sympathetically. Infrared radiation also has a frequency range, so when visible sunlight (higher frequency energy) comes in and hits the surface of the planet, that energy warms the surface. The surface then emits lower frequency energy as heat (IR) back up through the atmosphere.

The capacity of these molecules to vibrate (the “wobbling”) is “tuned” like the guitar string and when infrared radiation in the right frequency interacts with these gases, the molecule vibrates sympathetically. What they’re doing is absorbing and re-emitting that IR heatenergy. The difference with the dominant molecules, like oxygen (O2) and nitrogen (N2), is they can’t vibrate in this same manner nor at the same frequency ranges, thus they are invisible to IR.

That is the fundamental physics of climate change: the vibrational modes of greenhouse gases acting to absorb and scatter heat energy in the atmosphere. This was a cutting-edge discovery of the mid-19th century but now an indisputable fact of science. Scientists have empirically measured, modeled, and applied these facts in numerous ways for well over a century.

Ocean acidification spreading rapidly in Arctic Ocean,

March 9, 2017

International team reports ocean acidification spreading rapidly in Arctic Ocean, EurekAlert, 28 Feb 17, UNIVERSITY OF DELAWARE  Ocean acidification (OA) is spreading rapidly in the western Arctic Ocean in both area and depth, according to new interdisciplinary research reported in Nature Climate Changeby a team of international collaborators, including University of Delaware professor Wei-Jun Cai.

The research shows that, between the 1990s and 2010, acidified waters expanded northward approximately 300 nautical miles from the Chukchi slope off the coast of northwestern Alaska to just below the North Pole. Also, the depth of acidified waters was found to have increased, from approximately 325 feet to over 800 feet (or from 100 to 250 meters).

“The Arctic Ocean is the first ocean where we see such a rapid and large-scale increase in acidification, at least twice as fast as that observed in the Pacific or Atlantic oceans,” said Cai, the U.S. lead principal investigator on the project and Mary A.S. Lighthipe Professor of Earth, Ocean, and Environment at UD.

“The rapid spread of ocean acidification in the western Arctic has implications for marine life, particularly clams, mussels and tiny sea snails that may have difficulty building or maintaining their shells in increasingly acidified waters,” said Richard Feely, NOAA senior scientist and a co-author of the research. Sea snails called pteropods are part of the Arctic food web and important to the diet of salmon and herring. Their decline could affect the larger marine ecosystem.

Among the Arctic species potentially at risk from ocean acidification are subsistence fisheries of shrimp and varieties of salmon and crab.

Other collaborators on the international project include Liqi Chen, the Chinese lead principal investigator and scientist with the Third Institute of Oceanography of State Oceanic Administration of China; and scientists at Xiamen University, China and the University of Gothenburg, Sweden, among other institutions…….

Arctic ocean ice melt in the summer, once found only in shallow waters of depths less than 650 feet or 200 meters, now spreads further into the Arctic Ocean.

“It’s like a melting pond floating on the Arctic Ocean. It’s a thin water mass that exchanges carbon dioxide rapidly with the atmosphere above, causing carbon dioxide and acidity to increase in the meltwater on top of the seawater,” said Cai. “When the ice forms in winter, acidified waters below the ice become dense and sink down into the water column, spreading into deeper waters.”https://www.eurekalert.org/pub_releases/2017-02/uod-itr022717.php

Possibility of drastic cooling in North Atlantic

March 9, 2017

Drastic cooling in North Atlantic beyond worst fears, scientists warn https://www.theguardian.com/environment/2017/feb/24/drastic-cooling-north-atlantic-beyond-worst-fears-scientists-warn

Climatologists say Labrador Sea could cool within a decade before end of this century, leading to unprecedented disruption, reports Climate News Network, Guardian,  , 25 Feb 17, For thousands of years, parts of northwest Europe have enjoyed a climate about 5C warmer than many other regions on the same latitude. But new scientific analysis suggests that that could change much sooner and much faster than thought possible.

Climatologists who have looked again at the possibility of major climate change in and around the Atlantic Ocean, a persistent puzzle to researchers, now say there is an almost 50% chance that a key area of the North Atlantic could cool suddenly and rapidly, within the space of a decade, before the end of this century.

That is a much starker prospect than even the worst-case scientific scenario proposed so far, which does not see the Atlantic ocean current shutdown happening for several hundred years at least.

A scenario even more drastic (but fortunately fictional) was the subject of the 2004 US movie The Day After Tomorrow, which portrayed the disruption of the North Atlantic’s circulation leading to global cooling and a new Ice Age.

To evaluate the risk of extreme climate change, researchers from the Environnements et Paléoenvironnements Océaniques et Continentaux laboratory (CNRS/University of Bordeaux, France), and the University of Southamptondeveloped an algorithm to analyse the 40 climate models considered by the Fifth Assessment Report.

The findings by the British and French team, published in the Nature Communications journal, in sharp contrast to the IPCC, put the probability of rapid North Atlantic cooling during this century at almost an even chance – nearly 50%.

Current climate models foresee a slowing of the meridional overturning circulation (MOC), sometimes known also as the thermohaline circulation, which is the phenomenon behind the more familiar Gulf Stream that carries warmth from Florida to European shores. If it did slow, that could lead to a dramatic, unprecedented disruption of the climate system.

In 2013, drawing on 40 climate change projections, the IPCC judged that this slowdown would occur gradually, over a long period. Its findings suggested that fast cooling of the North Atlantic during this century was unlikely.

But oceanographers from EU emBRACE had also re-examined the 40 projections by focusing on a critical spot in the northwest of the North Atlantic: the Labrador Sea.

The Labrador Sea is host to a convection system ultimately feeding into the ocean-wide MOC. The temperatures of its surface waters plummet in the winter, increasing their density and causing them to sink. This displaces deep waters, which bring their heat with them as they rise to the surface, preventing the formation of ice caps.

The algorithm developed by the Anglo-French researchers was able to detect quick sea surface temperature variations. With it they found that seven of the 40 climate models they were studying predicted a total shutdown of convection, leading to abrupt cooling of the Labrador Sea by 2C to 3C over less than 10 years. This in turn would drastically lower North Atlantic coastal temperatures.

But because only a handful of the models supported this projection, the researchers focused on the critical parameter triggering winter convection: ocean stratification. Five of the models that included stratification predicted a rapid drop in North Atlantic temperatures.

The researchers say these projections can one day be tested against real data from the international OSnap project, whose teams will be anchoring scientific instruments within the sub-polar gyre (a gyre is any large system of circulating ocean currents).

If the predictions are borne out and the North Atlantic waters do cool rapidly over the coming years, the team says, with considerable understatement, climate change adaptation policies for regions bordering the North Atlantic will have to take account of this phenomenon.

NASA project – Oceans Melting Greenland (OMG) studies future sea level rise

March 9, 2017

OMG measurements of Greenland give us a glimpse of future sea rise https://www.skepticalscience.com/omg-greenland-sea-level-rise.html 24 February 2017 by John Abraham  If you meet a group of climate scientists, and ask them how much sea levels will rise by say the year 2100, you will get a wide range of answers. But, those with most expertise in sea level rise will tell you perhaps 1 meter (a little over three feet). Then, they will immediately say, “but there is a lot of uncertainty on this estimate.” It doesn’t mean they aren’t certain there will be sea level rise – that is guaranteed as we add more heat in the oceans. Here, uncertainty means it could be a lot more or a little less.

Why are scientists not certain about how much the sea level will rise? Because there are processes that are occurring that have the potential for causing huge sea level rise, but we’re uncertain about how fast they will occur. Specifically, two very large sheets of ice sit atop Greenland and Antarctica. If those sheets melt, sea levels will rise hundreds of feet.

Parts of the ice sheets are melting, but how much will melt and how fast will the melting occur? Are we talking decades? Centuries? Millennia? Scientists really want to know the answer to this question. Not only is it interesting scientifically, but it has huge impacts on coastal planning.

One reason the answer to this question is illusive is that melting of ice sheets can occur from above (warm air and sunlight) or from below (warm ocean waters). In many instances, it’s the melting from below that is most significant – but this melting from below is really hard to measure.

With hope we will have a much clearer sense of ice sheet melting and sea level rise because of a new scientific endeavor that is part of a NASA project – Oceans Melting Greenland (OMG). This project has brought together some of the best oceanographers and ice experts in the world. The preliminary results are encouraging and are discussed in two recent publications here and here.

In the papers, the authors note that Greenland ice loss has increased substantially in recent decades. It now contributes approximately 1/3 to total sea level rise. The authors want to know whether this contribution will change over time and they recognize that underwater processes may be the most important to study. In fact, they note in their paper:

Specifically, our goal is improved understanding of how ocean hydrographic variability around the ice sheet impacts glacial melt rates, thinning and retreat.

In plain English, they want to know how water flow around Greenland affects the ice melt.

Their experiments are measuring a number of key attributes. First, yearly changes in the temperature of ocean water near Greenland. Second, the yearly changes to the glaciers on Greenland that extend into the ocean waters. Third, they are observing marine topography (the shape of the land underneath the ocean surface).

The sea floor shape is quite complicated, particularly near Greenland. Past glaciers carved deep troughs in the sea floor in some areas, allowing warm salty water to reach huge glaciers that are draining the ice sheet. As lead OMG investigator Josh Willis said:

What’s interesting about the waters around Greenland is that they are upside down. Warm, salty water, which is heavy, sits below a layer of cold, fresh water from the Arctic Ocean. That means the warm water is down deep, and glaciers sitting in deep water could be in trouble.

As the warm water attacks marine glaciers (glaciers that extend into the ocean), the ice tends to break and calve, retreating toward land. In some cases, the glaciers retreat until their grounding line coincides with the shore. But in other cases the undulating surface allows warm water to wear the glacier underside for long distances and thereby increase the risk of large calving events.

Oftentimes, when glaciers near the coast break off they uncork other ice that can then more easily flow into the oceans.

Click here to read the rest

Mid-20th Century sea ice loss might have been masked by air pollution

March 9, 2017

Air pollution may have masked mid-20th Century sea ice loss https://www.sciencedaily.com/releases/2017/02/170223124327.htm February 23, 2017

Source:
American Geophysical Union
Summary:
Humans may have been altering Arctic sea ice longer than previously thought, according to researchers studying the effects of air pollution on sea ice growth in the mid-20th Century.

Humans may have been altering Arctic sea ice longer than previously thought, according to researchers studying the effects of air pollution on sea ice growth in the mid-20th Century. The new results challenge the perception that Arctic sea ice extent was unperturbed by human-caused climate change until the 1970s.

Scientists have observed Arctic sea ice loss since the mid-1970s and some climate model simulations have shown the region was losing sea ice as far back as 1950. In a new study, recently recovered Russian observations show an increase in sea ice from 1950 to 1975 as large as the subsequent decrease in sea ice observed from 1975 to 2005. The new observations of mid-century sea ice expansion led researchers behind the new study to the search for the cause.

The new study supports the idea that air pollution is to blame for the observed Arctic sea ice expansion. Particles of air pollution that come primarily from the burning of fossil fuels may have temporarily hidden the effects of global warming in the third quarter of the 20th Century in the eastern Arctic, the researchers say.

These particles, called sulfate aerosols, reflect sunlight back into space and cool the surface. This cooling effect may have disguised the influence of global warming on Arctic sea ice and may have resulted in sea ice growth recorded by Russian aerial surveys in the region from 1950 through 1975, according to the new research.

“The cooling impact from increasing aerosols more than masked the warming impact from increasing greenhouse gases,” said John Fyfe, a senior scientist at Environment and Climate Change Canada in Victoria and a co-author of the new study accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union.

To test the aerosol idea, researchers used computer modeling to simulate sulfate aerosols in the Arctic from 1950 through 1975. Concentrations of sulfate aerosols were especially high during these years before regulations like the Clean Air Act limited sulfur dioxide emissions that produce sulfate aerosols.

The study’s authors then matched the sulfate aerosol simulations to Russian observational data that suggested a substantial amount of sea ice growth during those years in the eastern Arctic. The resulting simulations show the cooling contribution of aerosols offset the ongoing warming effect of increasing greenhouse gases over the mid-twentieth century in that part of the Arctic. This would explain the expansion of the Arctic sea ice cover in those years, according to the new study.

Aerosols spend only days or weeks in the atmosphere so their effects are short-lived. The weak aerosol cooling effect diminished after 1980, following the enactment of clean air regulations. In the absence of this cooling effect, the warming effect of long-lived greenhouse gases like carbon dioxide has prevailed, leading to Arctic sea ice loss, according to the study’s authors.

The new study helps sort out the swings in Arctic sea ice cover that have been observed over the last 75 years, which is important for a better understanding of sea ice behavior and for predicting its behavior in the future, according to Fyfe.

The new study’s use of both observations and modeling is a good way to attribute the Arctic sea ice growth to sulfate aerosols, said Cecilia Bitz, a sea ice researcher at the University of Washington in Seattle who has also looked into the effects of aerosols on Arctic ice. The sea ice record prior to satellite images is “very sparse,” added Bitz, who was not involved in the new study.

Bitz also points out that some aerosols may have encouraged sea ice to retreat. Black carbon, for instance, is a pollutant from forest fires and other wood and fossil fuel burning that can darken ice and cause it to melt faster when the sun is up — the opposite effect of sulfates. Also, black carbon emissions in some parts of the Arctic are still quite common, she said.


Story Source:

Materials provided by American Geophysical Union.

Will global warming accelerate, due to the Interdecadal Pacific Oscillation, “El Tío” (the uncle)

March 9, 2017

Meet El Niño’s cranky uncle that could send global warming into hyperdrive, The Conversation, Research Fellow in Climate and Water Resources, University of Melbourne, Climate Extremes Research Fellow, University of Melbourne                                 , Science Fellow, Met Office Hadley Centre   Professor of Atmospheric Science, University of MelbourneSenior Research Scientist, CSIRO, PhD student, University of Melbourne      February 6, 2017

You’ve probably heard about El Niño, the climate system that brings dry and often hotter weather to Australia over summer.

You might also know that climate change is likely to intensify drought conditions, which is one of the reasons climate scientists keep talking about the desperate need to reduce greenhouse gas emissions, and the damaging consequences if we don’t.

El Niño is driven by changes in the Pacific Ocean, and shifts around with its opposite, La Niña, every 2-7 years, in a cycle known as the El Niño Southern Oscillation or ENSO.

But that’s only part of the story. There’s another important piece of nature’s puzzle in the Pacific Ocean that isn’t often discussed.

It’s called the Interdecadal Pacific Oscillation, or IPO, a name coined by a study which examined how Australia’s rainfall, temperature, river flow and crop yields changed over decades.

Since El Niño means “the boy” in Spanish, and La Niña “the girl”, we could call the warm phase of the IPO “El Tío” (the uncle) and the negative phase “La Tía” (the auntie).

These erratic relatives are hard to predict. El Tío and La Tía phases have been compared to a stumbling drunk. And honestly, can anyone predict what a drunk uncle will say at a family gathering?

What is El Tío?

Like ENSO, the IPO is related to the movement of warm water around the Pacific Ocean. Begrudgingly, it shifts its enormous backside around the great Pacific bathtub every 10-30 years, much longer than the 2-7 years of ENSO.

The IPO’s pattern is similar to ENSO, which has led climate scientists to think that the two are strongly linked. But the IPO operates on much longer timescales.

We don’t yet have conclusive knowledge of whether the IPO is a specific climate mechanism, and there is a strong school of thought which proposes that it is a combination of several different mechanisms in the ocean and the atmosphere.

Despite these mysteries, we know that the IPO had an influence on the global warming “hiatus” – the apparent slowdown in global temperature increases over the early 2000s……….

Since about the year 2000, some of the excess heat trapped by greenhouse gases has been getting buried in the deep Pacific Ocean, leading to a slowdown in global warming over about the last 15 years. It appears as though we have a kind auntie, La Tía perhaps, who has been cushioning the blow of global warming. For the time being, anyway.

The flip side of our kind auntie is our bad-tempered uncle, El Tío. He is partly responsible for periods of accelerated warming, like the period from the late 1970s to the late 1990s.

The IPO has been in its “kind auntie” phase for well over a decade now. But the IPO could be about to flip over to El Tío. If that happens, it is not good news for global temperatures – they will accelerate upwards……….

more work needs to be done to predict the next shift in the IPO and climate change. This is the topic of a new set of experiments that are going to be part the next round of climate model comparisons.

With further model development and new observations of the deep ocean available since 2005, scientists will be able to more easily answer some of these important questions.

Whatever the case, cranky old El Tío is waiting just around the corner. His big stick is poised, ready to give us a massive hiding: a swift rise in global temperatures over the coming decades. https://theconversation.com/meet-el-ninos-cranky-uncle-that-could-send-global-warming-into-hyperdrive-72360

National Academies of Science Around the World have issued Joint Statements on Climate Change

February 1, 2017

Skeptical Science 27 January 2017  This is a re-post from Significant Figures by Peter Gleick

National academies of sciences from around the world have published formal statements and declarations acknowledging the state of climate science, the fact that climate is changing, the compelling evidence that humans are responsible, and the need to debate and implement strategies to reduce emissions of greenhouse gases. Not a single national science academy disputes or denies the scientific consensus around human-caused climate change. A few examples of joint academy statements since 2000 on climate are listed here. Many national academies have, in addition, published their own reports and studies on climate issues. These are not included here.

The Science of Climate Change (Statement of 17 National Science Academies, 2001)

http://science.sciencemag.org/content/292/5520/1261

Following the release of the third in the ongoing series of international reviews of climatescience conducted by the Intergovernmental Panel on Climate Chang (IPCC), seventeen national science academies issued a joint statement, entitled “The Science of Climate Change,” acknowledging the IPCC study to be the scientific consensus on climate changescience.

The seventeen signatories were:

  • Australian Academy of Sciences
  • Royal Flemish Academy of Belgium for Sciences and the Arts
  • Brazilian Academy of Sciences
  • Royal Society of Canada
  • Caribbean Academy of Sciences
  • Chinese Academy of Sciences
  • French Academy of Sciences
  • German Academy of Sciences, Leopoldina
  • Indian National Science Academy
  • Indonesian Academy of Sciences
  • Royal Irish Academy
  • Accademia Nazionale dei Lincei (Italy)
  • Academy of Sciences Malaysia
  • Academy Council of the Royal Society of New Zealand
  • Royal Swedish Academy of Sciences
  • Turkish Academy of Sciences
  • Royal Society (UK)

Joint science academies’ statement: Global response to climate change(Statement of 11 National Science Academies, 2005)

http://nationalacademies.org/onpi/06072005.pdf

Eleven national science academies, including all the largest emitters of greenhouse gases, signed a statement that the scientific understanding of climate change was sufficiently strong to justify prompt action. The statement explicitly endorsed the IPCC consensus and stated:

“…there is now strong evidence that significant global warming is occurring. The evidence comes from direct measurements of rising surface air temperatures and subsurface ocean temperatures and from phenomena such as increases in average global sea levels, retreating glaciers, and changes to many physical and biological systems. It is likely that most of the warming in recent decades can be attributed to human activities (IPCC 2001). This warming has already led to changes in the Earth’s climate.”………

Joint science academies’ statement: Global response to climate change(Statement of 11 National Science Academies, 2005)

http://nationalacademies.org/onpi/06072005.pdf………

Joint science academies’ statement on Growth and responsibility: sustainability, energy efficiency and climate protection (Statement of 13 National Science Academies, 2007)

http://www.pik-potsdam.de/aktuelles/nachrichten/dateien/G8_Academies%20Declaration.pdf……..

A joint statement on sustainability, energy efficiency, and climate change(Statement of 13 individual National Science Academies and the African Academy of Sciences, 2007)

http://www.interacademies.net/File.aspx?id=4825………..

Zmian klimatu, globalnego ocieplenia i ich alarmujących skutkow: “Climate change, global warming and its alarming consequences” (Statement of the Polish Academy of Sciences, December 2007)

http://bit.ly/2jwgtNL………

Joint Science Academies’ Statement: Climate Change Adaptation and the Transition to a Low Carbon Society (Statement of 13 National Academies of Sciences, June 2008)

http://www.nationalacademies.org/includes/climatechangestatement.pdf……..

Climate change and the transformation of energy technologies for a low carbon future (Statement of 13 National Academies of Sciences, May 2009)

http://www.leopoldina.org/en/press/press-releases/press-release/press/713/………

Health Effects of Climate Change (Statement of the Inter Academy Medical Panel/42 National Academies of Sciences, 2010)

http://www.leopoldina.org/de/publikationen/detailansicht/publication/health-effects-of-climate-change-2010/………

Climate Change: Evidence and Causes (Joint Statement of the Royal Society and the U.S. National Academy of Sciences, February 2014)

http://nas-sites.org/americasclimatechoices/events/a-discussion-on-climate-change-evidence-and-causes/……..

Position de l’Académie sur les Changements Climatiques (Statement of the Académie Royale des Science, des Lettres & des Beaux-Arts de Belgique, November 12, 2014)

https://t.co/SZT9VvU8vx………

U.K. Science Communiqué on Climate Change (Joint Statement of the Royal Society and member organizations, July 2015)

https://royalsociety.org/~/media/policy/Publications/2015/21-07-15-climate-communique.PDF…….

Facing critical decisions on climate change (Joint Statement of the European Academies Science Advisory Council and its 29 members, 2015)

http://www.leopoldina.org/de/publikationen/detailansicht/publication/facing-critical-decisions-on-climate-change-in-2015/

Facing critical decisions on climate change in 2015

The science of climate change reported by the IPCC Fourth Assessment (2007) and Fifth Assessment (2014) have been thoroughly evaluated by numerous national academies (e.g. Royal Society/National Academy of Sciences, Royal Swedish Academy of Sciences) and by international bodies. Advances in science and technology have increased our knowledge of how to mitigate climate change, uncertainties in the scientific analysis continue to be addressed, co-benefits of mitigation to health have been revealed, and new business opportunities have been found. EASAC remains concerned, however, that progress in turning this substantial evidence base into an international policy response has so far failed to match the full magnitude and urgency of the problem

Even if emissions of GHG stopped altogether, existing concentrations of GHG in the atmosphere would continue to exert a warming effect for a long time. Whatever measures are put in place to reduce the intensity of global human-induced climate forcing, building resilience through adaptation will be necessary to provide more resilience to the risks already emerging as a result of climate change…

Signatories/Members of the European Academies Science Advisory Council

  • Academia Europaea
  • All European Academies (ALLEA)
  • The Austrian Academy of Sciences
  • The Royal Academies for Science and the Arts of Belgium
  • The Bulgarian Academy of Sciences
  • The Croatian Academy of Sciences and Arts
  • The Czech Academy of Sciences
  • The Royal Danish Academy of Sciences and Letters
  • The Estonian Academy of Sciences
  • TheCouncil of Finnish Academies
  • The German Academy of Sciences Leopoldina
  • The Academy of Athens
  • The Hungarian Academy of Sciences
  • The Royal Irish Academy
  • The Accademia Nazionale dei Lincei
  • The Latvian Academy of Sciences
  • The Lithuanian Academy of Sciences
  • The Royal Netherlands Academy of Arts and Sciences
  • The Norwegian Academy of Science and Letters
  • The Polish Academy of Sciences
  • The Academy of Sciences of Lisbon
  • The Romanian Academy
  • The Slovak Academy of Sciences
  • The Slovenian Academy of Sciences and Arts
  • The Spanish Royal Academy of Sciences
  • The Royal Swedish Academy of Sciences
  • The Swiss Academies of Arts and Sciences
  • The Royal Society
  • The Federation of European Academies of Medicine (FEAM) (Observer)

[This list is not a complete summary of the many individual or joint statements of national academies of sciences. Please send additions and corrections to pgleick@pacinst.orghttps://www.skepticalscience.com/joint-statements-on-climate-change-from-nas-around-world.html