Blog Archive

Saturday, September 23, 2017

John Abraham: It takes just 4 years to detect human warming of the oceans

Our new paper illustrates the rapid, consistent warming of Earth’s oceans

Bondi Beach in Sydney, Australia.
 Bondi Beach in Sydney, Australia. Photograph: Mick Tsikas/AAP
by John Abraham, "Climate Consensus  The 97%," The Guardian, September 20, 2017

We’ve known for decades that the Earth is warming, but a key question is, how fast? Another key question is whether the warming is primarily caused by human activities. If we can more precisely measure the rate of warming and the natural component, it would be useful for decision makers, legislators, and others to help us adapt and cope. Indeed, added ocean heat content underlies the potential for dangerous intense hurricanes.
An answer to the “how fast?” question was partly answered in an Opinion piece just published on Eos.org, the daily online Earth and space science news site, by scientists from China, Europe, and the United States. I was fortunate enough to be part of the research team.
Study authors Dr. John Fasullo, Dr. Kevin Trenberth, and Dr. Lijing Cheng (co-authors Timothy Boyer, John Abraham, and Karina von Shuckmann not shown).
 Study authors Dr. John Fasullo, Dr. Kevin Trenberth, and Dr. Lijing Cheng (co-authors Timothy Boyer, John Abraham, and Karina von Shuckmann not shown).

To measure how fast the globe is warming, we focused on the extra heat that is being trapped in the climate. The key to measuring the extra heat is by comparing the incoming and outgoing energy – just like you watch your bank account, keeping track of income and expenses to tell whether your bank balance will increase or not.
Okay so how do we measure these incoming and outgoing flows? In our view, the best way is in the oceans. We know that the oceans absorb almost all of the excess heat – so, perhaps we can detect energy increases in ocean waters.
Measuring the oceans is challenging. They are vast and they are deep – measurements can be noisy. Detecting a long-term trend (a signal) within the noise can be a challenge. But this challenge is exactly what we focused on. We wanted to know how large the signal-to-noise ratio is for ocean heat measurements, because this would tell us how many years of data are needed to detect warming. Can we detect global warming with one year of measurements? With a decade? Or do we need multiple decades of measurements to be sure the climate is changing?
Our work shows that scientists need less than 4 years of ocean heat measurements to detect a warming signal. This is much shorter than the nearly three decades of measurements that would be required to detect global warming if we were to use temperatures of air near the Earth’s surface. It is also slightly better than the nearly 5 years of sea level rise data that are needed for detecting a long-term trend. This means that the warming is not natural but rather stems from the human-induced climate change, primarily from increases in heat-trapping gases in the atmosphere.
This finding should help change the way we talk about global warming. Normally, scientists and the public wait for the official annual “global temperatures” to be released (every January or February) by major research groups like NASA, NOAA, and the Hadley Centre in the UK. Avid consumers of global warming news often use these air temperatures to “prove” or “disprove” global warming. If it was hot last year, “It's global warming!” If last year was cool, “Global warming is over!” 
But the year-to-year fluctuations of air temperatures are predominantly associated with El Niño and weather variability and mislead those who use any one year as climate-change proof. We saw the impact of fluctuations over the past two decades, when a slowing of the rise of global surface temperatures led to false claims that global warming had “stopped” or that there was a “hiatus.” No such cessation occurred for ocean heat content.
Hence, global ocean heat content data isn’t so noisy. It represents the total thermal energy in the ocean waters and is now known with a high degree of certainty (see the figure below), in part because scientists have improved ocean temperature sensing methods and increased the number of sensors throughout the ocean waters. 
Increases in ocean heat content since 1950s.
Pinterest
 Increases in ocean heat content since 1950s. Illustration: Cheng, L., K. E. Trenberth, J. Fasullo, J. Abraham, T. P. Boyer, K. von Schuckmann, and J. Zhu (2017), Taking the pulse of the planet, Eos, Vol. 98.

According to our analysis, the top 10 warmest years of ocean heat content are all in the most recent decade (following 2006), with the last two years being the hottest. The heat storage in the ocean corresponds to 3 × 1023 Joules (a 3 with twenty-three zeroes after it) since 1960. Prior to the 1980s, values are not as well known, and the global record is unreliable prior to about 1960.
In the most recent 25 years, the Earth has gained approximately 0.7 Watts for every square meter of surface area. That may not sound like much, but think about how many square meters are required to cover the surface of the Earth. To put these numbers in perspective, the heat increase in the oceans since 1992 is about 2,000 times the total net generation of electricity in the USA in the past decade.
We believe, and argue, that ocean heat content is the key to quantifying how fast the climate is changing, and it has important implications for regional patterns of climate. According to Trenberth:
A key reason for the exceptionally active Atlantic hurricane season this year is because of the regional build-up of ocean heat, along with its global warming component, that fuels hurricanes.
“Ocean Heat Content” should become a standard metric not only for measuring climate change but for testing our computer models that are used to predict the future climate.

Saturday, August 26, 2017

Exxon misled the public about climate change, Harvard study shows



FOR IMMEDIATE RELEASE
AUGUST 23, 2017
CONTACT:
Kyle Moler

Exxon misled the public about climate change, Harvard study shows

Cambridge, MA In the first comprehensive, academically peer-reviewed analysis of ExxonMobil’s 40-year history of climate-change communications, researchers at Harvard University have concluded that the company has misled the public about climate change.

A review of 187 public and internal Exxon documents found that, accounting for reasonable doubt, 83% of peer-reviewed papers authored by Exxon scientists and 80% of the company’s internal communications acknowledge that climate change is real and human-caused. In contrast, only 12% of Exxon’s advertorials directed at the public do so, with 81% instead expressing doubt.

“On the question of whether ExxonMobil misled non-scientific audiences about climate science, our analysis supports the conclusion that it did,” says the academic study published today by Drs. Geoffrey Supran and Naomi Oreskes in the journal Environmental Research Letters. [Link to paper: http://iopscience.iop.org/article/10.1088/1748-9326/aa815f or bit.ly/ExxonPaper. Paper published online at this address at 02:00 a.m. ET, August 23, 2017.]

These findings come as the Attorneys General of New York and Massachusetts and the Securities and Exchange Commission continue to investigate the oil and gas company for potentially misleading investors and the public about the risks of climate change. Exxon employees and shareholders have already filed lawsuits against the company on these grounds.

The year-long study is an expansive, quantitative, independent corroboration of the findings of investigative journalists, who ExxonMobil have accused of using “deliberately cherry-picked statements.” This latest work goes further, showing both that ExxonMobil knew about the basic realities of climate change decades ago and that the company simultaneously communicated positions that were at odds with this knowledge to the general public.

The authors explain that their research was prompted by ExxonMobil’s challenge to the public: “Read all of these documents and make up your own mind.”

“This paper takes up that challenge,” the Harvard authors write.

The researchers used an established social science method called content analysis to characterize 187 of ExxonMobil’s public and private publications about climate change, spanning 1977 to 2014. These included ExxonMobil’s peer-reviewed and non-peer-reviewed scientific work, internal company memos, and paid, editorial-style advertisements (“advertorials”) in The New York Times. Content analysis allowed Supran and Oreskes to evaluate the number of documents expressing different viewpoints on climate change and thereby to quantify the consistency of ExxonMobil’s climate communications.

The research looks at ExxonMobil’s positions on climate change as real, human-caused, serious, and solvable, and at the company’s acknowledgment of the risks of fossil-fuel assets becoming ‘stranded’ by climate policy. In each case, the article concludes, “available documents show a systematic discrepancy between what ExxonMobil’s scientists and executives discussed about climate change privately and in academic circles and what it presented to the general public.” The authors found the topic of stranded assets to be “discussed and sometimes quantified in 24 documents of various types, but absent from advertorials.”

In short, the paper finds, “ExxonMobil contributed quietly to the science and loudly to raising doubts about it.” The company’s academic publications had an average readership of tens to hundreds, whereas advertorial readerships were likely in the millions.

The Harvard paper is also explicit about its limitations. “We acknowledge that textual analysis is inherently subjective: words have meaning in context.” Yet, the authors argue, “While one might disagree about the interpretation of specific words, the overall trends between document categories are clear.”

To make these trends fully auditable, the peer-reviewed paper includes 121-pages of “Supplementary Information” [link to be added]. Here, the authors have tabulated all quotations, from all 187 analyzed documents, substantiating their conclusions.

The paper’s acknowledgments state that this research was supported by Harvard University Faculty Development Funds and by the Rockefeller Family Fund.

Other interesting findings of the analysis

  • Most of ExxonMobil’s climate science has been spearheaded by one person.
“In 1986, scientist Haroon Kheshgi joined ER&E [Exxon Research and Engineering], and was henceforth ExxonMobil’s principal (and only consistent) academic author, co-authoring 72% (52/72) of all analyzed peer-reviewed work (79% since his hiring). Indeed, the metadata title of the “Exxon Mobil Contributed Publications” file is Haroon’s CV.(See section 4.1.1 of paper for details.)

  • The Harvard study finds that “ExxonMobil’s advertorials included several instances of explicit factual misrepresentation.”
For example, “...an ExxonMobil advertorial in 2000 directly contradicted the IPCC and presented very misleading data, according to the scientist who produced the data.” (See section 3.1.5 of paper for details.)

  • Advertorials were part of an ExxonMobil climate-change communication plan
“Mobil/ExxonMobil bought AGW advertorials in the NYT specifically to allow the public to know where we stand.Readerships were likely in the millions. The company took out an advertorial every Thursday between 1972 and 2001. They paid a discounted price of roughly $31,000 (2016 USD) per advertorial and bought one-quarter of all advertorials on the Op-Ed page, towering over the other sponsors according to reviews of Mobil’s advertorials by Brown, Waltzer, and Waltzer.” (See section 4 of paper for details.)
  • ExxonMobil’s early estimates of the “carbon budget”  which implies risks of stranded fossil fuel assets, many have argued — “are within a factor of two of contemporary estimates.” (See section 3.4.2 of paper for details.)

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

LONDON 
– 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.”