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Boomerangs versus Javelins: The Impact of Polarization on Climate Change Communication

Filed under: — mike @ 7 June 2016

Guest commentary by Jack Zhou, Nicholas School of the Environment, Duke University

For advocates of climate change action, communication on the issue has often meant “finding the right message” that will spur their audience to action and convince skeptics to change their minds. This is the notion that simply connecting climate change to the right issue domains or symbols will cut through the political gridlock on the issue. The difficulty then lies with finding these magic bullet messages, figuring out if they talk about climate change in the context of with national security or polar bears or passing down a clean environment to future generations.

On highly polarized issues like climate change, however, communicating across the aisle may be more difficult than simply finding the right message. Here, the worst case scenario is not simply a message failing to land and sending you back to the drawing board. Instead, any message that your audience disagrees with may polarize that audience even further in their skepticism, leaving you in a worse position than you began. As climate change has become an increasingly partisan issue in American politics, this means that convincing Republicans to reject the party line of climate skepticism may be easier said than done.
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The Early Anthropocene Hypothesis: An Update

Filed under: — mike @ 15 March 2016

Guest post from Bill Ruddiman, University of Virginia

For over a decade, paleoclimate scientists have argued whether the warmth of the last several thousand years was natural or anthropogenic. This brief comment updates that debate, also discussed earlier at RC: Debate over the Early Anthropogenic Hypothesis (2005) and An Emerging View on Early Land Use (2011). The graph below outlines the evolution of that debate through 4 phases.


In phase 1 (the 1900’s), scientists viewed Holocene climate change as driven only by natural causes until the industrial era began. But by the late 1990’s, ice core data revealed late Holocene GHG rises unlike trends in previous interglaciations. Two hypotheses proposed natural causes for the CO2 increase: carbonate compensation (Broecker et al., 1999, 2001) and coral-reef construction (Ridgewell et al., 2003).

In phase 2 (2001-2003), the early anthropogenic hypothesis (EAH) challenged natural explanations for the anomalous late Holocene CO2 (and CH4) rises, attributing them to the spread of early agriculture thousands of years ago.

In phase 3 (2004-2008), several arguments were advanced against the EAH:
* too few people lived millennia ago to have had a significant influence on land clearance, GHG emissions and climate;
* a (proposed) interglacial stage 11 analog for the Holocene suggested that thousands of years of natural warmth still remain in the current interglaciation;
* the weak decrease in ice core δ13CO2 during the last 7000 years did not permit extensive deforestation which would have released abundant 12C -rich carbon.
Papers by myself, my co-authors at Wisconsin, and others during phase 3 rebutted some of these criticisms, but community opinion remained divided.

Phase 4 (2009-2016) has seen a major shift in viewpoint of published papers: 30 papers favor aspects of the EAH, 6 papers oppose it, and 5 are in the middle. Most of the phase 4 papers that oppose the hypothesis or are ‘in the middle’ are based on modeling studies. Many of the 30 supporting papers are broad-scale compilations of archaeological and paleoecological evidence:
* The average GHG trends from 7 previous interglaciations show CO2 and CH4 decreases, in contrast to the late Holocene increases;
* Interglacial stage 19, the closest Holocene analog, shows decreases in CH4 and CO2, and the CO2 decrease closely matches the 2003 EAH prediction;
* CH4 emissions from Asian rice paddies account for 70% of the observed CH4 rise from 5000 to 1000 years ago
* historical data show that early per-capita land use was at least 4 times larger than assumed in several phase-3 land use simulations
* a recent land use simulation based on historical evidence accounts for more than half the CO2 anomaly originally proposed in the EAH;
* pollen evidence shows nearly complete deforestation in north-central Europe before the industrial era began;
* δD and δ18O trends show anomalous late Holocene warmth compared to cooling trends in prior interglaciations, in agreement with A-OGCM simulations of the warming effect of the anthropogenic CO2 and CH4 trends.

Anyone seeking more detail on this issue should contact for pdf copies of the recent 2016 Ruddiman et al. paper in Reviews of Geophysics and an invited paper just submitted to Oxford University Press that summarizes the history of this debate, with full references to the papers shown in the table.

How Likely Is The Observed Recent Warmth?

Filed under: — mike @ 25 January 2016

With the official numbers now in 2015 is, by a substantial margin, the new record-holder, the warmest year in recorded history for both the globe and the Northern Hemisphere. The title was sadly short-lived for previous record-holder 2014. And 2016 could be yet warmer if the current global warmth persists through the year.

One might well wonder: just how likely is it that we would be seeing these sort of streaks of record-breaking temperatures if not for human-caused warming of the planet?

Precisely that question was posed by several media organizations a year ago, in the wake of the then-record 2014 temperatures. Various press accounts reported odds anywhere from 1-in-27 million to 1-in-650 million that the observed run of global temperature records (9 of the 10 warmest years and 13 of the 15 warmest years each having had occurred since 2000) might have resulted from chance alone, i.e. without any assistance from human-caused global warming.

My colleagues and I suspected the odds quoted were way too slim. The problem is that each year was treated as though it were statistically independent of neighboring years (i.e. that each year is uncorrelated with the year before it or after it), but that’s just not true. Temperatures don’t vary erratically from one year to the next. Natural variations in temperature wax and wane over a period of several years. More »

An Online University Course on the Science of Climate Science Denial

Filed under: — mike @ 22 April 2015

Guest post from John Cook, University of Queensland

For many years, RealClimate has been educating the public about climate science. The value of climate scientists patiently explaining the science and rebutting misinformation directly with the public cannot be overestimated. When I began investigating this issue, my initial searches led me here, which was invaluable in increasing my understanding of our climate and making sense of misinformation. RealClimate has inspired and empowered a host of climate communicators such as myself to step forward and help make climate science more accessible to the general public.

To further the work of educating the public, and empowering people to communicate the realities of climate change, the Skeptical Science team has collaborated with The University of Queensland to develop a MOOC, Making Sense of Climate Science Denial. MOOC stands for Massive (we’ve already had thousands of students sign up from over 130 countries) Open (available for free to everyone) Online (web-based, no software required) Course.

The course examines the science of climate science denial. Why do a small but vocal minority reject the scientific evidence for climate change? What techniques do they use to cast doubt on the science? And we examine the all-important question – based on scientific research, how should we respond to science denial?

Several strands of research in cognitive psychology, educational research and a branch of psychology called “inoculation theory” all point the way to neutralising the influence of science denial. The approach is two-fold: communicate the science but also explain how that science can be distorted.

So our course looks at the most common climate myths you’re likely to encounter online or in the media. We examine myths casting doubt on the reality of global warming. We explore the many human fingerprints on climate change. We look at the messages from past climate change and what climate models tell us about the future. And we look at how climate change is impacting every part of society and the environment. As we examine myths touching on all these parts of climate science, we shine the spotlight on the fallacies and techniques used to distort the science.


As well as our short video lectures debunking climate myths, we also interviewed many of the world’s leading scientists. I had the privilege to speak to Ben Santer, Katharine Hayhoe, Richard Alley, Phil Jones, Naomi Oreskes and let’s not forget my long, fascinating conversation with Michael Mann. I was also lucky enough to interview Sir David Attenborough at the Great Barrier Reef. We spoke to both climate scientists and social scientists who study the psychology of climate science denial. Some of the most powerful moments from those interviews came when the scientists described the attacks they’d personally experienced because of their climate research:

Our MOOC starts next Tuesday, April 28. It’s a free online course hosted by the not-for-profit edX (founded by Harvard University & MIT). It runs for 7 weeks, requiring 1 to 2 hours per week. You can enroll at

A Scientific Debate

Filed under: — mike @ 13 April 2015

Guest posting from Bill Ruddiman, University of Virginia

Recently I’ve read claims that some scientists are opposed to AGW but won’t speak out because they fear censure from a nearly monolithic community intent on imposing a mainstream view. Yet my last 10 years of personal experience refute this claim. This story began late in 2003 when I introduced a new idea (the ‘early anthropogenic hypothesis’) that went completely against a prevailing climatic paradigm of the time. I claimed that detectable human influences on Earth’s surface and its climate began thousands of years ago because of agriculture. Here I describe how this radically different idea was received by the mainstream scientific community.

Was my initial attempt to present this new idea suppressed? No. I submitted a paper to Climatic Change, then edited by Steve Schneider, a well-known climate scientist and AGW spokesman. From what I could tell, Steve was agnostic about my idea but published it because he found it an interesting challenge to the conventional wisdom. I also gave the Emiliani lecture at the 2003 December American Geophysical Union (AGU) conference to some 800 people. I feel certain that very few of those scientists came to my talk believing what my abstract claimed. They attended because they were interested in a really new idea from someone with a decent career reputation. The talk was covered by many prominent media sources, including the New York Times and The Economist. This experience told me that provocative new ideas draw interest because they are provocative and new, provided that they pass the key ‘sniff test’ by presenting evidence in support of their claims.

Did this radical new idea have difficulty receiving research funding? No. Proposals submitted to the highly competitive National Science Foundation (NSF) with John Kutzbach and Steve Vavrus have been fully funded since 2004 by 3-year grants. Even though the hypothesis of early anthropogenic effects on climate has been controversial (and still is for some), we crafted proposals that were carefully written, tightly reasoned, and focused on testing the new idea. As a result, we succeeded against negative funding odds of 4-1 or 5-1. One program manager told me he planned to put our grant on a short list of ‘transformational’ proposals/grants that NSF had requested. That didn’t mean he accepted our hypothesis. It meant that he felt that our hypothesis had the potential to transform that particular field of paleoclimatic research, if proven correct.

Were we able to get papers published? Yes. As any scientist will tell you, this process is rarely easy. Even reviewers who basically support what you have to say will rarely hand out ‘easy-pass’ reviews. They add their own perspective, and they often point out useful improvements. A few reviews of the 30-some papers we have published during the last 11 years have come back with extremely negative reviews, seemingly from scientists who seem deeply opposed to anything that even hints at large early anthropogenic effects. While these uber-critical reviews are discouraging, I have learned to put them aside for a few days, give my spirits time to rebound, and then address the criticisms that are fair (that is, evidence-based), explain to the journal editor why other criticisms are unfair, and submit a revised (and inevitably improved) paper. Eventually, our views have always gotten published, although sometimes only after considerable effort.

The decade-long argument over large early anthropogenic effects continues, although recent syntheses of archeological and paleoecological data have been increasingly supportive. In any case, I continue to trust the scientific process to sort this debate out. I suggest that my experience is a good index of the way the system actually operates when new and controversial ideas emerge. I see no evidence that the system is muffling good new ideas.

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