Climate change chronicles from NASA

By Erik Conway, NASA Jet Propulsion Laboratory

A new paper has revisited the question of whether there’s a consensus among climate scientists about the reality of anthropogenic (human-caused) global warming (AGW). The study, by John Cook, of the University of Queensland’s Global Change Institute in Australia and the Skeptical Science site, and several co-authors, confirms that climate scientists have not only accepted the existence of global warming, but also its human causation, as a matter of fact for the last two decades.

Drawing from 11,944 climate science abstracts from scientific journals between 1991 and 2011, the team found 66.4 percent of the abstracts expressed no opinion, 32.6 percent explicitly endorsed AGW, 0.7 percent rejected it and 0.3 percent expressed uncertainty on the cause of global warming.  Then the authors invited a subset of these papers’ authors to place their own papers into the same categories that Cook and his collaborators had used. These authors overwhelmingly endorsed the statement that most of the past century’s warming was caused by human greenhouse gas emissions.

This isn’t a terribly surprising result. As the authors acknowledge, Naomi Oreskes found the same overwhelming consensus back in 2004 (though with a much smaller sample size). The methodology underlying the two papers differs, especially in that Cook and colleagues used a web-based, randomized abstract distribution and review process — and polled individual authors as a second check on their categorization. But the result, like several survey-based papers published in the last few years, is essentially the same. Climate scientists agree that humans are causing climate change, and they have agreed on this for some time.

Perhaps the one new finding in this paper is the quantitative demonstration that the consensus existed by 1991. Again, I don’t find this surprising. The National Academy of Science’s 1979 report, "Carbon Dioxide and Climate: A Scientific Assessment," found “no reason to doubt that climate change will result, and no reason to believe that those changes will be negligible” from a continuing buildup of carbon dioxide in Earth’s atmosphere. Oreskes’ results also indicate that the consensus among publishing researchers was in place by the early 1990s. But further quantitative confirmation that these earlier studies were not far out on a limb is nice to have.

This latest publication by Cook and co. has resulted in a kerfuffle among some of the climate-change-friendly bloggers that I think is worth mentioning. One blogger I follow closely, Dan Kahan of the Cultural Cognition Project at Yale University, has expressed unhappiness about it on the grounds that re-determining or re-emphasizing the existence of consensus doesn’t advance climate science communication. Kahan and I, like most social scientists, are opponents of what’s known as the “deficit model” of science communication, which posits that people are empty vessels into which one can simply pour facts. Rather, I believe that people accept, or reject, new information mostly on the basis of their pre-existing knowledge and beliefs. So merely telling the average citizen that 97 percent of climate scientists believe that humans are causing climate change isn’t likely to change many minds about the issue.

But some polls and market research have shown that, for quite a few people, their views about government action change when they think the science is settled. This was a key finding of market research sponsored by the Western Fuels Association, a coal industry trade association, in the early 1990s — just as the scientific consensus on anthropogenic warming was emerging — and a major reason why they funded campaigns to persuade the American people that the science was unsettled. The idea was (and remains) to challenge the science to prevent action. And it was, of course, the guiding idea behind tobacco industry disinformation campaigns as well. So to the extent that this strategy works, it’s important to continue to point out that it is based on a fallacy.

I do think there’s more that Cook et al. could draw out of the data they’ve collected. I have a hypothesis that different disciplines within climate science reached consensus at different times: radiative transfer specialists in the 1980s, atmospheric scientists by the mid-1990s, physical oceanographers and cryosphere researchers in the early 2000s, etc. I don’t have the data to test that hypothesis quantitatively, but I think Cook and his collaborators now do. I hope they take on the challenge, as that would be a worthwhile expansion of our knowledge about the historical development of this important science. 

References/Further Reading:

John Cook et al., “Quantifying the consensus on anthropogenic global warming in the scientific literature,” Environ. Res. Lett. 8, 024024 (2013), doi:10.1088/1748-9326/8/2/024024.

Naomi Oreskes, “The Scientific Consensus on Climate Change,” Science Vol. 306, no. 5702, p. 1686 (3 December 2004), doi: 10.1126/science.1103618.

Ad Hoc Study Group on Carbon Dioxide and Climate, "Carbon Dioxide and Climate: A Scientific Assessment," National Academy of Sciences, Washington, DC (1979), quote from p. viii.

Imagine there are no people. Imagine a planet where the sea level is about five to 40 meters (16 to 131 feet) higher than normal. Imagine a planet that is hotter and wetter. Imagine, worldwide, it’s roughly 3 to 4 degrees Celsius (5.4 to 7.2 degrees Fahrenheit) warmer than today. And the North and South poles are even warmer still – as much as 10 degrees Celsius (18 degrees Fahrenheit) hotter than today.

Welcome to the Pliocene. That was the Earth about three to five million years ago, very different to the Earth we inhabit now. But in at least one respect it was rather similar. This is the last time that carbon dioxide (CO₂) levels were as high as they are today.

On May 9, 2013, CO₂ levels in the air reached the level of 400 parts per million (ppm). This is the first time in human history that this milestone has been passed. A preliminary daily average reading of 400.03 ppm was reported by the U.S. National Oceanic and Atmospheric Administration (NOAA), which operates the Mauna Loa Observatory in Hawaii where these measurements are made. While 400 sounds like just another number whose meaning is hard to grasp – similar to, say, world population recently hitting seven billion – these things do resonate, says Dr. Gavin Schimdt of NASA’s Goddard Institute for Space Studies. “People respond to anniversaries – why is 10 years after 9/11 more worthy of note than nine or 11 years? The importance of crossing 400 ppm is simply that it allows us to mark the occasion, and to demonstrate to the future that we knew where we were headed."

CO₂ is the most important man-made greenhouse gas, which means (in a simple sense) that it acts like a blanket trapping heat near the surface of the Earth. It comes from the burning of fossil fuels such as coal, oil and natural gas, as well as deforestation. The level of CO₂ in the atmosphere has risen from around 317 ppm in 1958 (when Charles David Keeling began making his historical measurements at Mauna Loa) to 400 ppm today. It’s projected to reach 450 ppm by the year 2040.

One of the problems is that CO₂ lingers, both in the atmosphere and in the oceans (where it is being absorbed and acidifying the waters, with potentially big impacts on marine life). More than half of the CO₂ is removed from the atmosphere within a century, but about 20 percent remains in the air for many thousands of years. Because of slow removal processes, even if we massively reduced our emissions of CO₂ right now, atmospheric CO₂ would continue to increase in the long-term. The CO₂ we emit today, and that we have emitted since the advent of the Industrial Revolution, has long-term consequences that future generations will have to live with.

Some scientists, like NASA’s James Hansen, argue that CO₂ must be limited to around 350 ppm in order to prevent “dangerous” climate change. As Hansen wrote in a 2008 paper, “If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted, paleoclimate evidence and ongoing climate change suggest that CO₂ will need to be reduced … to at most 350 ppm.”

To some, crossing the threshold of 400 ppm is a signal that we are now firmly seated in the “Anthropocene,” a human epoch where people are having major and lasting impacts on the planet. Because of the long lifetime of CO₂, to others it means we are marching inexorably towards a “point of no return,” into territory that is unknown for the human race.

To hear what NASA scientists are saying about this milestone, click here.

In this series on "Big Fat Planet," we answer reader-submitted questions about Earth's climate. The following is from Dr. Duane Waliser, who specializes in climate dynamics and modeling. He is the chief scientist of JPL's Earth Science and Technology Directorate and an adjunct professor in the Atmospheric and Oceanic Sciences Department at UCLA.

Question: How is climate change shaping the type of space exploration NASA does?

As global climate change becomes more evident, NASA’s satellite program for studying and monitoring our home planet becomes increasingly important. There are two key areas toward which NASA satellite measurements can contribute:

1.  Monitoring changes in the Earth’s climate.  Global climate change occurs slowly relative to weather and even to the change of seasons throughout the year. Changes known to be related to global climate change--increased atmospheric carbon dioxide and other greenhouse gases (including water vapor), sea level rise, and the melting of Arctic sea ice and the Greenland and Antarctic ice sheets--are so gradual that it takes many years, even decades, to characterize and quantify them. 

Given that satellite missions typically last on the order of three to 10 years, NASA often needs to consider launching copies of some instruments, as current versions age and fail. Continuity in our satellite observations is important for maintaining long records of key climate indicators, such as those listed above.  Having long and continuous records of these is critical for monitoring the effects of climate change, helping determine how we can best adapt to them, and assessing whether measures to limit its effects are working as expected.

2.  Improving our understanding of global climate change key processes. Simply monitoring some of the climate change indicators listed above doesn’t provide enough information for scientists to fully understand and characterize the problem and consequences. 

For example, only observing sea level rise doesn’t illuminate all the key processes that might be involved in determining the rate at which it is rising; these include sea level rise, the melting of ice sheets and glaciers, warming of the ocean, the continents’ and shorelines’ slow response to ice sheet melting and sea level rise, etc.  Similarly, it is critical to understand how water vapor and clouds respond to climate change, as these help determine the amount of future temperature warming that might be expected to result from increasing the amount of greenhouse gases in the atmosphere.

Knowing "how the Earth’s climate works" is vital to making projections of future warming and the associated impacts using very sophisticated computer models of the Earth’s climate.  For such projections to be useful, they have to accurately represent the Earth’s climate system.

I spend a lot of time asking students, audiences at speaking engagements, and other members of the public about their thoughts on science and I’ve noticed a theme that runs across all education levels, from deans and education administrators to lawyers and college students. “Sure, I like science,” people sigh, or “I used to like science when I was a kid.”

Often I hear positive descriptions of science: “It’s creative, fun, open, and interesting,” muddled with tired, old stereotypes: “Science is sterile, movies portray scientists as loners lacking social skills, it’s too complicated, I’m just not good at science.”

In the last few years, there has been an upsurge of websites, outreach opportunities, new media products and treatises about ways to improve public perception and public engagement in science. Nevertheless, the relationship between the public and the scientific community remains estranged. Scientific and academic communities have the habit of focusing inward, seeking engagement from those who are already engaged, while overlooking a portion of the public that feels cut off.

Professors are still in the outdated habit of failing half the class as a protocol to promote rigor, and our scientific community is made up of those who found a way to conform in this atmosphere. Failed students don’t merely vanish: they become our neighbors, our fellow citizens. They influence society. As a community of scientists and science educators, are they failing us or are we the ones who are failing them? Are we closing the door to people who may bring something creative, are we locking ourselves in?

Science-themed videos land in my inbox daily, tagged with notes like “this is great” on products that are boring or unmemorable and have few clicks. It’s not enough for us to pat ourselves on the back for our excellent work; it’s the public that ultimately judges the quality of our products. If you’re presenting a talk and you look at the faces of your audience and their eyes are glazed or they’re texting, then your talk is boring. If your online product isn’t getting thousands of hits then you need to re-evaluate and make changes. You will know if your message resonates in a meaningful way if you get invited back, referred, liked, shared, and remembered.

We need to maintain the rigorous content of scientific principles while at the same time engage a broader audience so that the scientific message resonates in a more meaningful way for more people. Having a Ph.D. and doing research is one way to participate in science, but not the only way. Yes, our students and our public must raise the bar on their intellectual capacity, and who wouldn’t want to participate in expanding their brainpower? But it’s us—the scientists, communicators, and educators—who also need to raise our own standards and expand our own capacity to find a way to connect.

Dr. Josh Willis, ocean guru at NASA's Jet Propulsion Laboratory, spoke to TV channel KCET recently about what sea level rise will mean for California and our coasts. Here's the interview.

An interesting recent paper from Dr. Son Nghiem at NASA’s Jet Propulsion Laboratory and colleagues finds that the bottom of the Arctic Ocean controls the pattern of sea ice thousands of feet above on the water’s surface. The seafloor topography exerts its control not only locally, in the Bering, Chukchi, Beaufort, Barents and Greenland Seas, but also spanning hundreds to thousands of miles across the Arctic Ocean. 

How? The seafloor influences the distribution of cold and warm waters in the Arctic Ocean where sea ice can preferentially grow or melt. Geological features on the ocean bottom also guide how the sea ice moves, along with influence from surface winds.

Interestingly, the study also links the bottom of the Arctic Ocean with cloud patterns up in the sky. The ocean bottom affects sea ice cover, which affects the amount of vapor coming from the surface of the ocean out into the air, which in turn influences cloud cover.

The researchers, who also come from NASA's Goddard Space Flight Center, the Applied Physics Laboratory and the National/Naval Ice Center in the U.S., use sea ice maps taken from space with NASA’s QuickSCAT satellite, as well as measurements from drifting buoys in the Arctic Ocean. They compare the sea ice and seafloor topography patterns to identify the connection between the two.

Bottom line:

Since the seafloor does not change significantly over many years, sea ice patterns can form repeatedly and persist around certain underwater geological features. So computer models need to incorporate these features in order to improve their forecasts of how ice cover will change over the short- and long-term. This ‘memory’ of the underwater topography could help refine our predictions of what will happen to ice in the Arctic as the climate changes.

Source:

“Seafloor Control on Sea Ice,” S. V. Nghiem, P. Clemente-Colon, I.G. Rigor, D.K. Hall & G. Neumann, Deep Sea Research Part II: Topical Studies in Oceanography, Volumes 77-80, pp 52-61 (2012).

Climate change makes headlines, but not so much box office or TV hits. In an effort to inject more realistic climate-related story arcs into the silver screen, NASA climate experts and Hollywood entertainment writers and producers came together last month to chat. A bus of writers and producers (from TV series such as Grimm and Curious George) dropped in on NASA’s Jet Propulsion Laboratory to hear about topics ranging from the impact of global warming on the Amazon rainforest to potentially new sources of sustainable energy involving microbes living inside termites. And in an “Entertaining Climate Change” event held in Los Angeles, producers, writers, filmmakers and artists came to listen to Dr. Jim Hansen, one of NASA’s best-known climatologists, talk about how real people are being affected by climate change now. They also learned how NASA’s suite of satellites monitors climate change around the planet and how we visualize that information.

Writers John Vorhaus (left) and Cindy Lichtman listen to Dr. Sassan Saatchi of NASA JPL discuss the effects of climate change on forest ecosystems. Photo by Howard Pasamanick.

Writer Spiro Skentzos listens to a presentation.

The tour was organized by Hollywood, Health and Society (HH&S), a program of the University of Southern California’s Annenberg School for Communication and Journalism based in Los Angeles. The tour was part of a new collaboration between climate.nasa.gov and the Annenberg School. HH&S hooks up entertainment industry professionals with accurate, timely information that can be used in health- and climate-related plotlines — information that is unusual, compelling and dramatic, but based on real stories about real people and places. Global instability, infectious diseases and drought are all examples of real-life storylines that are linked to climate change and that could make for thought-provoking entertainment.

The Hollywood, Health and Society group poses with a model of the Mars Rover Curiosity.

At present, TV storylines about climate change are “close to zero”, explained HH&S Director Sandra de Castro Buffington. An HH&S TV monitoring project earlier this year looked at more than 3,000 storylines used in the top 28 scripted TV shows, and found that only 24 of them — less than one percent — dealt with climate change, and most of them only peripherally.

This effort is trying to change that. While you may not see “CSI Climate”, “Attack of the Frankenstorms” or “Extreme Weather Makeover” anytime soon, hopefully TV programs and movies will soon begin to reflect the reality of climate change.