Blog Archive

Saturday, July 29, 2017

New research may resolve a climate ‘conundrum’ across the history of human civilization

The new study also confirms the planet is warming 20 times faster than Earth’s fastest natural climate change
Stalagmites and stalactites in the caves of Diros in Greece.
Stalagmites and stalactites in the caves of Diros in Greece. Photograph: Alamy Stock Photo

by Dana Nuccitelli, "Climate Consensus - the 97%," The Guardian, June 14, 2017

Earth’s last ice age ended about 12,000 years ago. The warmer and more stable climate that followed allowed for the development of agriculture and the rise of human civilization. This important period encompassing the past 12,000 years is referred to as the Holocene geological epoch. It also created a “conundrum” for climate scientists, because global temperatures simulated by climate models didn’t match reconstructions from proxy data.
To be specific, the overall temperature change during the Holocene matched pretty well in reconstructions and models, but the pattern didn’t. The best proxy reconstruction from a 2013 paper led by Shaun Marcott estimated more warming than models from 12,000 to 7,000 years ago. Then over the past 7,000 years, Marcott’s reconstruction estimated about 0.5 °C cooling while model simulations showed the planet warming by about the same amount.
A new paper led by Jonathan Baker may help to resolve that discrepancy. The scientists examined stalagmites from a cave in the southern Ural Mountains of Russia. The ratio of oxygen isotopes in the stalagmites can be used to estimate past winter temperatures. The Marcott study had one known shortcoming – the proxy temperature data they used mostly represented the summer season. And as Baker explained, changes in the Earth’s orbital cycles have caused cooling in the Northern Hemisphere summer and winter warming during the Holocene:

Because our orbit is elliptical, we’re not always the same distance from the sun. About 10,000 years ago, Earth was closest to the sun during summer and farthest during winter. Today it is the opposite. Based on this variable alone, we would expect winter warming and summer cooling in the Northern Hemisphere (and vice versa in the Southern Hemisphere) over the last 10,000 years.
During the period from 15,000 to 7,000 years ago, temperatures were rising because large ice sheets were disappearing. That was especially true in the summer because back then, the Earth was closest to the sun during that season. So the Marcott temperature reconstruction, which was predominantly based on summer temperature proxies, estimated a lot of warming from 15,000 to 7,000 years ago (more than in model simulations), then a small cooling thereafter, while models simulate a slight warming over the past 7,000 years due to a slow rise in greenhouse gases.
The stalagmite data in the Baker study show that winter temperatures behaved differently and can reconcile the discrepancies between the Marcott reconstruction and model simulations. This suggests that the climate models are right – Earth’s surface temperature warmed rapidly at the end of the last ice age, from about 17,000 to 7,000 years ago, then the rate of warming slowed as the climate stabilized. However, it didn’t reverse into a cooling trend, because atmospheric greenhouse gas levels were rising.
Then of course came the Industrial Revolution 200 years ago, and carbon dioxide levels consequently shot up due to humans burning fossil fuels. As a result, temperatures have spiked as well. Over the past 130 years, global surface temperatures have risen about 20 times faster than when the Earth transitioned out of the last ice age. Over the past 40 years, the rate of global warming has been 3 times faster yet.
And that’s in comparison to Earth’s fastest natural climate change, when it’s transitioning from an ice age to a warm period. Over the past 7,000 years, when human civilization was able to develop and thrive, Earth’s temperatures and climate were quite stable. The temperature change during the past 7,000 years was about 0.5 °C. Humans have caused that much warming in just the past 25 years. If we follow through with the Paris agreement and manage to limit global warming to 2 °C over a 200-year period, in that best-case scenario the Earth would still warm 20 times faster than a natural ice age transition. If we fail to cut carbon pollution, that rate could speed to more than 50 times faster than Earth’s fastest natural climate change.
There are several important points we can take from the Baker study. First, climate models are able to simulate climate changes over the history of human civilization fairly accurately. Second, when there’s a discrepancy between data and models, people have a tendency to distrust the models, but sometimes the problem lies more in the data. Third, if not for the human influence, the climate would continue the stable conditions of the past 7,000 years, during which time human civilization developed and thrived.
Fourth and most importantly, humans are in the process of destabilizing the climate, and we’re already causing global warming at a rate 20 times faster than Earth’s fastest natural climate change. That’s why climate scientists are so concerned, and why the Paris agreement is so important.

USGS Projects Large Loss of Alaska Permafrost by 2100 (and it won't stop there!)

Using statistically modeled maps drawn from satellite data and other sources, U.S. Geological Survey scientists have projected that the near-surface permafrost that presently underlies 38% of boreal and arctic Alaska would be reduced by 16-24% by the end of the 21st Century under widely accepted climate scenarios.
from the USGS, November 30, 2015
Using statistically modeled maps drawn from satellite data and other sources, U.S. Geological Survey scientists have projected that the near-surface permafrost that presently underlies 38% of boreal and arctic Alaska would be reduced by 16-24% by the end of the 21st century under widely accepted climate scenarios. Permafrost declines are more likely in central Alaska than northern Alaska. 
Northern latitude tundra and boreal forests are experiencing an accelerated warming trend that is greater than in other parts of the world. This warming trend degrades permafrost, defined as ground that stays below freezing for at least two consecutive years. Some of the adverse impacts of melting permafrost are changing pathways of ground and surface water, interruptions of regional transportation, and the release to the atmosphere of previously stored carbon. 
“A warming climate is affecting the Arctic in the most complex ways,” said Virginia Burkett, USGS Associate Director for Climate and Land Use Change. “Understanding the current distribution of permafrost and estimating where it is likely to disappear are key factors in predicting the future responses of northern ecosystems to climate change.” 
In addition to developing maps of near-surface permafrost distributions, the researchers developed maps of maximum thaw depth, or active-layer depth, and provided uncertainty estimates. Future permafrost distribution probabilities, based on future climate scenarios produced by the Intergovernmental Panel on Climate Change (IPCC), were also estimated by the USGS scientists. Widely used IPCC climate scenarios anticipate varied levels of climate mitigation action by the global community. 
These future projections of permafrost distribution, however, did not include other possible future disturbances in the future, such as wildland fires. In general, the results support concerns about permafrost carbon becoming available to decomposition and greenhouse gas emission. 
[Below, be sure to check out the size of the blue area in the north.]
The research has been published in Remote Sensing of Environment. The current near-surface permafrost map is available via ScienceBase.
Current probability of near-surface permafrost in Alaska. Future scenarios.

Friday, July 28, 2017

A profile of 2017 Roger Revelle Medal winner climate scientist Kevin Trenberth

Readers, please note the Trenberth quote just under the name of this blog. He's been a leader on climate science and overwhelmingly deserves this award.

A profile of award-winning climate scientist Kevin Trenberth

Kevin Trenberth - recent award winner - is one of the world’s foremost climate scientists
Dr. Kevin Trenberth at the March for Science on 22 April 2017 in Denver, Colorado.
Dr. Kevin Trenberth at the March for Science on 22 April 2017 in Denver, Colorado.

by John Abraham, "Climate Consensus - the 97%," The Guardian, July 27, 2017

The American Geophysical Union - the pre-eminent organization of Earth scientists - presents annual awards to celebrate the achievements of scientists. The awards, which are often named after famous historical scientists, reflect the contributions to science in the area of the award namesake. With the 2017 award winners just announced, it’s appropriate to showcase one of the winners here. 
The 2017 winner of the Roger Revelle medal is Dr. Kevin E. Trenberth. One of the most well-known scientists in the world, he is certainly the person most knowledgeable about climate change that I know.
Kevin Trenberth
 Kevin Trenberth Photograph: Robert Tjalondo

The Roger Revelle award is given to an honoree who has made outstanding contributions to the understanding of the atmosphere and its interactions with other parts of the climate system. Named after Roger Revelle, who was critical in bringing the idea of human-caused climate change to the scientific community, it is amongst the highest honors. Revelle wrote regarding increasing carbon dioxide in the atmosphere in 1957:
human beings are now carrying out a large scale geophysical experiment
Kevin Trenberth
 Kevin Trenberth Photograph: Robert Tjalondo
Certainly the other scientists nominated were of incredible quality. Why was Kevin granted the award? I cannot answer this for certain because I was not on the committee, but it’s possible that he won strictly because of his scientific contributions.
Dr. Trenberth is a leading voice in the concept of Earth Energy Imbalance (which is really the rate of global warming). He also pioneered research related to the interactions of the atmosphere with the oceans, particularly the El Niño/La Niña cycle. He has worked on advancements to climate models and to experimental observations of climate. Another major area of contribution is the changes in precipitation with climate change, and especially the frequency and intensity of extremes. He has also changed the approaches to attribution of human-caused climate change.
But perhaps Dr. Trenberth won the award because of the sheer volume and impact of his scholarship. He is closing in on 70,000 citations to his work. This puts him near the top of the list worldwide for impact.
Or maybe he won because of his tireless efforts in service to the scientific community, with leadership roles in the IPCC, the World Climate Research Programme, NOAA, and other groups. Or lastly, it could be because he is tireless as both a researcher and a communicator. Dr. Trenberth can be heard or read almost weekly in major newspapers, magazine articles, radio and television shows. When reporters need complex climate science explained, he is a go-to person, and has been for years.
His personal life is interesting, too. Born in New Zealand, he studied mathematics before embarking on meteorology. His time in New Zealand provided him with a different geographic perspective than his American and European colleagues. New Zealand is more impacted by certain climate oscillations, like fluctuations in the temperature of the Pacific Ocean surface waters. Certainly these experiences affected his climate views.
Growing up, family, school, and sports – he was a top rugby player - were important. He was somehow able to balance these three pillars of life without sacrifice to his academics. Born into a family of very modest means, Kevin had to make his own fortunes. His early academic performance resulted in financial scholarships for school. 
After some time spent in the New Zealand army, he was ready to embark upon his scientific career. After winning a New Zealand government fellowship to do his doctorate at MIT, he met his future wife Gail who was as ever energetic, smart, and involved in life as was Kevin. They had a daughter in New Zealand, and, after moving to the U.S. as a professor at the University of Illinois, began fostering, which led to the adoption of their second child.
Somehow Kevin and his wife kept both career and family center in their lives and Kevin’s reputation as a top-rated scientist increased. He moved to the National Center for Atmospheric Research in 1984. His scientific work and his public communication efforts meant that he became a frequent target of groups that try to deny human-caused climate change or diminish its importance. The problem with Kevin is, he knows so much you can just assume he is smarter than you. 
Well-known contrarians such as Richard Lindzen, Roy Spencer, and John Christy have had their works rebutted by Trenberth for technical errors. Trenberth has also crossed paths with vocal down-players of climate change like Roger Pielke Jr., who reportedly threatened Trenberth by email. Pielke Jr. was working for Nate Silver’s 538 website; his actions lead to Nate Silver stating “We had candid conversations with Michael Mann and Kevin Trenberth (about the emails). We made clear that Roger’s conversations with them did not reflect FiveThirtyEight’s editorial values.” More details of the altercation are available here.
Why would I write about this aspect of Trenberth’s career? Because it shows that he has suffered slings and arrows for his tireless work. He has spent his career being honest about the limits of our knowledge of the Earth’s climate but also being clear about our certainty of human-caused climate change. His reward for this tireless service to society has been attacks on his research and his person. However, he has been impeccable in character and scholarship. The ill-advised who tangle with Trenberth have discovered they are on the short end of the intellectual battle.
It is my view that the AGU, by granting awards such as these to scientists, effectively encourage others to reach the highest standards in their profession.
Interested readers can go here to read about the other AGU award winners for the 2017 year.

Saturday, July 22, 2017

Asian temperatures could rise disastrously

Profligate fossil fuel use could cause Asian temperatures to rise by 6 °C, bringing floods and food shortages for hundreds of millions.
by Tim Radford, Climate News Network, July 21, 2017

– Unrestrained climate change could have serious consequences by forcing Asian temperatures drastically upwards; it could limit economic growth and reverse recent human advances for hundreds of millions, according to a new study.
The Asian Development Bank and the Potsdam Institute for Climate Impact Research say in a new report that if humans continue to burn fossil fuels under the “business as usual” scenario, then global average temperatures could rise by 4 °C.
But over the landmass of Asia, summer temperatures could rise by 6 °C and high mountain nations such as Afghanistan, Tajikistan, Pakistan, and northwest China could register summer rises of 8 °C above historic levels. Heat-related deaths among the elderly are predicted to rise by 52,000 cases by 2050.
These devastating temperatures would be accompanied by more rain – although Pakistan and Afghanistan could become much drier – and greater vulnerability to flooding as typhoons and tropical cyclones increase in intensity.

Child hunger

Global flood losses, set at $6bn a year in 2005, could rise to $52bn by 2050, and 13 Asian cities are among the 20 worldwide that can expect the greatest flood losses in the next 30 years.
Food production could be hit and rice yields in south-east Asia, for example, could drop by 50%. Food shortages could increase the count of malnourished children in south Asia by 7m.
Coral reefs in the region could be devastated by mass bleaching. Sea levels could rise by 1.4 metres by 2100 and go on rising over the centuries by more than five metres.
“The global climate crisis is arguably the biggest challenge human civilisation faces in the 21st century, with the Asia and Pacific region at the heart of it all," said Bambang Susantono, of the Asian Development Bank.

“The Asian countries hold Earth's future in their hands. If they choose to protect themselves against dangerous climate change, they will help to save the entire planet”

“Home to two-thirds of the world's poor, and regarded as one of the most vulnerable regions to climate change, countries in Asia and the Pacific are at the highest risk of plummeting into deeper poverty – and disaster – if mitigation and adaptation efforts are not quickly and strongly implemented.”
Over the last 25 years, per capita income in Asia and the Pacific has grown tenfold: so too have the cities. The world has 71 cities with more than 5m inhabitants, and 33 of these are in Asia. These 33 are now home to 348m people. By 2030, they could be sheltering 483bn, a 40% growth in 15 years. By 2030, there could be another eight megacities, four in India.
But as wealth has increased, so has inequality. The poorest are most likely to be the greatest victims of unrestrained climate change.
“The Asian countries hold Earth's future in their hands. If they choose to protect themselves against dangerous climate change, they will help to save the entire planet,” said Hans Joachim Schellnhuber, director of the Potsdam Institute.

Crucial actor

“The challenge is twofold. On the one hand, Asian greenhouse gas emissions have to be reduced in a way that the global community can limit planetary warming to well below 2 °C, as agreed in Paris 2015.  
“Yet even adapting to 1.5 °C temperature rise is a major task. So, on the other hand, Asian countries have to find strategies for ensuring prosperity and security under unavoidable climate change within a healthy global development,” Professor Schellnhuber said.
“But note that leading the clean industrial revolution will provide Asia with unprecedented economic opportunities. And exploring the best strategies to absorb the shocks of environmental change will make Asia a crucial actor in 21st Century multilateralism.”

'Seemingly unbelievable' temperatures becoming more common in Arctic winters

Warm periods are bringing the temperature up by as much as 30 C in the middle of winter

The research vessel Lance sits in the Arctic sea ice on 17 February 2015.
The research vessel Lance sits in the Arctic sea ice on 17 February 2015. (Courtesy Paul Dodd/Norwegian Polar Institute)

by Jimmy Thomson, CBC News, July 12, 2017

Extreme warming events are blowing into the Arctic more frequently during the winter, and lasting longer, according to a new study from the American Geophysical Union. The storms have an effect on sea ice formation, and could even be linked to extreme weather in the south.
"The big takeaway for us was that these seemingly unbelievable winter temperatures close to the North Pole, close to 0 C, is not completely new — but in recent years, these patterns are increasing, and we're getting more of these storms," says lead author Dr. Robert Graham, of the Norwegian Polar Institute.
Normally, during the winter, temperatures in the High Arctic stay below –30 C. But, occasionally, a storm blows in from the Atlantic or Pacific Oceans, bringing warm air with it. The resulting extreme weather contributes to melting sea ice through high temperatures and accompanying high winds.
But the effects also last beyond the event itself. By adding snow that insulates the ice from the returning cold temperatures, the storms also prevent the ice from refreezing.
"In 2017, we had the record minimum sea ice extent in March. So these two things, we believe, are going hand in hand," says Graham.

Sea ice disappearing

A lack of sea ice can cause its own problems. Open water absorbs more heat than ice, so the ocean warms even faster. That, in turn, makes it more difficult for the ice to form the following year, causing a cascade of ecological effects throughout food webs.
Warming events have been recorded as far back as 1893, when explorer Fridtjof Nansen's Fram expedition spent four years drifting in the Arctic Ocean. During that trip, the crew recorded temperatures as high as –3.7 C in March, at 84 degrees north.
For this study, the authors also drew on half a century worth of data from drifting Soviet research stations on the polar ice, which, in 1956, recorded the first winter temperatures above –1 C at 85 degrees north.
Sea ice buoy
A 'snow buoy' embedded in the sea ice takes temperature readings.
More recent data came from modern sea ice buoys. 
Over the last century of data, the researchers found high temperatures were increasingly common, and increasingly long. The average length of a warm period around the North Pole has increased by 4.25 days each decade since 1980, and Graham expects the trend to continue to intensify in the future.
Some scientists have argued that the lack of sea ice has destabilized the jet stream, leading to cold weather sweeping south while warm southern weather pushes further north, meaning that strange winter events in the south, like ice storms in Texas and a persistent "blob" of warm water in the Pacific, may be related to the conditions in the Arctic.
"I think that this is kind of what we expect," says Graham, but cautions that that is not within the scope of the current study.
"It's something we want to look into in the future."

Wednesday, July 12, 2017

Larsen C breaks away

People can watch further developments here:,MODIS_Aqua_CorrectedReflectance_TrueColor(hidden),MODIS_Terra_CorrectedReflectance_TrueColor,VIIRS_SNPP_DayNightBand_ENCC,Coastlines&t=2017-07-12&z=3&v=-2570154.5783290304,937557.1566580613,-1783722.5783290304,1313877.1566580613

Sunday, July 9, 2017

Ben Santer, WaPo: I’m a climate scientist. And I’m not letting trickle-down ignorance win.

How to fight the Trump administration's darkness

Fact Checkers Glenn Kessler and Michelle Lee examine several of President Trump's claims from his speech announcing the U.S. withdrawal from the Paris climate accord on Thursday. (Video: Meg Kelly/Photo: Jabin Botsford/The Washington Post)

by Ben Santer, The Washington Post, July 5, 2017

I’ve been a mountaineer for most of my life. Mountains are in my blood. In my early 20s, while climbing in France, I fell into a crevasse on the Milieu Glacier, at the start of the normal route on the Aiguille d’Argentiere. Remarkably, I was unhurt. From the grip of the banded ice, I saw a thin slit of blue sky 120 feet above me. The math was simple: Climb 120 feet. If I reached that slit of blue sky, I would live. If I didn’t, I’d freeze to death in the cold and dark.
Now, more than 40 years later, it feels like I’m in a different kind of darkness — the darkness of the Trump administration’s scientific ignorance. This is just as real as the darkness of the Milieu Glacier’s interior and just as life-threatening. This time, I’m not alone. The consequences of this ignorance affect every person on the planet.
Imagine, if you will, that you spend your entire professional life trying to do one thing to the best of your ability. In my case, that one thing is to study the nature and causes of climate change. You put in a long apprenticeship. You spend years learning about the climate system, computer models of climate and climate observations. You start filling a tool kit with the statistical and mathematical methods you’ll need for analyzing complex data sets. You are taught how electrical engineers detect signals embedded in noisy data. You apply those engineering insights to the detection of a human-caused warming signal buried in the natural “noise” of Earth’s climate. Eventually, you learn that human activities are warming Earth’s surface, and you publish this finding in peer-reviewed literature.
You participate in rigorous national and international assessments of climate science. You try to put aside all personal filters, to be objective, to accommodate a diversity of scientific opinions held by your peers, by industry stakeholders, and by governments. These assessments are like nothing you’ve ever done before: They are peer review on steroids, eating up years of your life.
The bottom-line finding of the assessments is cautious at first. In 1995, the conclusion is this: “The balance of evidence suggests a discernible human influence on global climate.” These 12 words are part of a chapter on which you are first author. The 12 words change your life. You spend years defending the “discernible human influence” conclusion. You encounter valid scientific criticism. You also encounter nonscientific criticism from powerful forces of unreason, who harbor no personal animus toward you but don’t like what you’ve learned and published — it’s bad for their business.
Your peers are your fiercest critics. They are constantly kicking the tires. Show us that your “discernible human influence” results aren’t due to changes in the sun, or volcanic activity, or internal cycles in the climate system. Show us that your results aren’t due to some combination of these natural factors. Convince us that detection of a human fingerprint isn’t sensitive to uncertainties in models, data, or the statistical methods in your tool kit. Explain the causes of each and every wiggle in temperature records. Respond to every claim contradicting your findings.
So you jump through hoops. You do due diligence. You go down every blind alley, every rabbit hole. Over time, the evidence for a discernible human influence on global climate becomes overwhelming. The evidence is internally and physically consistent. It’s in climate measurements made from the ground, from weather balloons, and from space — measurements of dozens of different climate variables made by hundreds of different research groups around the world. You write more papers, examine more uncertainties, and participate in more scientific assessments. You tell others what you’ve done, what you’ve learned, and what the climatic “shape of things to come” might look like if we do nothing to reduce emissions of heat-trapping greenhouse gases. You speak not only to your scientific peers but also to a wide variety of audiences, some of which are skeptical about you and everything you do. You enter the public arena and make yourself accountable.
After decades of seeking to advance scientific understanding, reality suddenly shifts, and you are back in the cold darkness of ignorance. The ignorance starts at the top, with President Trump. It starts with untruths and alternative facts. The untruth that climate change is a “hoax” engineered by the Chinese. The alternative fact that “nobody really knows” whether climate change is real. These untruths and alternative facts are repeated again and again. They serve as talking points for other members of the administration. From the Environmental Protection Agency administrator, who has spent his career fighting climate change science, we learn the alternative fact that satellite data shows “a leveling off of warming ” over the past two decades. The energy secretary tells us the fairy tale that climate change is primarily due to “ocean waters and this environment that we live in.” Ignorance trickles down from the president to members of his administration, eventually filtering into the public’s consciousness.
Getting out of this metaphorical darkness is going to be tough. The administration is powerful. It has access to media megaphones and bully pulpits. It can abrogate international climate agreements. It can weaken national legislation designed to protect our air and water. It can challenge climate science and tell us that more than three decades of scientific understanding and rigorous assessments are all worthless. It can question the integrity and motives of climate scientists. It can halt satellite missions and impair our ability to monitor Earth’s climate from space. It can shut down websites hosting real facts on the science of climate change. It can deny, delay, defund, distort, dismantle. It can fiddle while the planet burns.
I have to believe that even in this darkness, though, there is still a thin slit of blue sky. My optimism comes from a gut-level belief in the decency and intelligence of the people of this country. Most Americans have an investment in the future — in our children and grandchildren, and in the planet that is our only home. Most Americans care about these investments in the future; we want to protect them from harm. That is our prime directive. Most of us understand that to fulfill this directive, we can’t ignore the reality of a warming planet, rising seas, retreating snow and ice, and changes in the severity and frequency of droughts and floods. We can’t ignore the reality that human actions are part of the climate change problem and that human actions must be part of the solution. Ignoring reality is not a viable survival strategy.
Trump has referred to a cloud hanging over his administration. The primary cloud I see is the self-created cloud of willful ignorance on the science of climate change. That cloud is a clear and present threat to the lives, livelihoods, and health of every person on the planet, now and in the future. This cloud could be easily lifted by the president himself.
For my own part, I don’t intend to spend the rest of my life in darkness or silently accepting trickle-down ignorance. I didn’t climb out of a crevasse on the Milieu Glacier for that.

Posts in June 2017