Scientific process

The Most Common Skeptical Arguments About Climate Change (from the Grist articles: How to Talk to a Climate Skeptic – see site for images)

Global warming is a hoax

Objection: Global warming is a hoax perpetrated by environmental extremists and liberals who want an excuse for more big government (and/or world government via the U.N.).

This is a common line, regardless of how ridiculous it is, so it should not go unanswered.

Answer: Here is a list of organizations that accept anthropogenic global warming as real and scientifically well-supported:

NASA’s Goddard Institute of Space Studies (GISS):
National Oceanic and Atmospheric Administration (NOAA):
Intergovernmental Panel on Climate Change (IPCC):
National Academy of Sciences (NAS):
State of the Canadian Cryosphere (SOCC) –
Environmental Protection Agency (EPA):
The Royal Society of the UK (RS) –
American Geophysical Union (AGU):
American Meteorological Society (AMS):
American Institute of Physics (AIP):
National Center for Atmospheric Research (NCAR):
American Meteorological Society (AMS):
Canadian Meteorological and Oceanographic Society (CMOS):

Every major scientific institution dealing with climate, ocean, and/or atmosphere agrees that the climate is warming rapidly and the primary cause is human CO2 emissions. In addition to that list, see also this joint statement (PDF) that specifically and unequivocally endorses the work and conclusions of the IPCC Third Assessment report. The statement was issued by:

Academia Brasiliera de Ciencias (Brazil)
Royal Society of Canada
Chinese Academy of Sciences
Academie des Sciences (France)
Deutsche Akademie der Naturforscher Leopoldina (Germany)
Indian National Science Academy
Accademia dei Lincei (Italy)
Science Council of Japan
Russian Academy of Sciences
Royal Society (United Kingdom)
National Academy of Sciences (United States of America)

You can also read this statement [PDF], which includes all the above signatories plus the following:

Australian Academy of Sciences
Royal Flemish Academy of Belgium for Sciences and the Arts
Caribbean Academy of Sciences
Indonesian Academy of Sciences
Royal Irish Academy
Academy of Sciences Malaysia
Academy Council of the Royal Society of New Zealand
Royal Swedish Academy of Sciences

But if scientists are too liberal and politicians too unreliable, perhaps you find the opinion of key industry representatives more convincing:

BP, the largest oil company in the UK and one of the largest in the world, has this opinion:

There is an increasing consensus that climate change is linked to the consumption of carbon based fuels and that action is required now to avoid further increases in carbon emissions as the global demand for energy increases.

Shell Oil (yes, as in oil, the fossil fuel) says:

Shell shares the widespread concern that the emission of greenhouse gases from human activities is leading to changes in the global climate.

Eighteen CEOs of Canada’s largest corporations had this to say in an open letter to the Prime Minister of Canada:

Our organizations accept that a strong response is required to the strengthening evidence in the scientific assessments of the Intergovernmental Panel on Climate Change (IPCC). We accept the IPCC consensus that climate change raises the risk of severe consequences for human health and security and the environment. We note that Canada is particularly vulnerable to the impacts of climate change.

Have the environazis seized the reigns of industrial power, in addition to infiltrating the U.N., the science academies of every developed nation, and the top research institutes of North America? That just doesn’t seem very likely.

There is no consensus

Objection: Climate is complicated and there are lots of competing theories and unsolved mysteries. Until this is all worked out, one can’t claim there is consensus on global warming theory. Until there is, we should not take any action.

This is similar to the “global warming is a hoax” article, but at least here we can narrow down just what the consensus is about.

Answer: Sure there are plenty of unsolved problems and active debates in climate science. But if you look at the research papers coming out these days, the debates are about things like why model predictions of outgoing longwave radiation at the top of the atmosphere in tropical latitudes differ from satellite readings, or how the size of ice crystals in cirrus clouds affect the amount of incoming shortwave reflected back into space, or precisely how much stratospheric cooling can be attributed to ozone depletion rather than an enhanced greenhouse effect.

No one in the climate science community is debating whether or not changes in atmospheric CO2 concentrations alter the greenhouse effect, or if the current warming trend is outside of the range of natural variability, or if sea levels have risen over the last century.

This is where there is a consensus.

Specifically, the “consensus” about anthropogenic climate change entails the following:

the climate is undergoing a pronounced warming trend beyond the range of natural variability;
the major cause of most of the observed warming is rising levels of the greenhouse gas CO2;
the rise in CO2 is the result of burning fossil fuels;
if CO2 continues to rise over the next century, the warming will continue; and
a climate change of the projected magnitude over this time frame represents potential danger to human welfare and the environment.

While theories and viewpoints in conflict with the above do exist, their proponents constitute a very small minority. If we require unanimity before being confident, well, we can’t be sure the earth isn’t hollow either.

This consensus is represented in the IPCC Third Assessment Report, Working Group 1 (TAR WG1), the most comprehensive compilation and summary of current climate research ever attempted, and arguably the most thoroughly peer reviewed scientific document in history. While this review was sponsored by the UN, the research it compiled and reviewed was not, and the scientists involved were independent and came from all over the world.

The conclusions reached in this document have been explicitly endorsed by …

Academia Brasiliera de Ciências (Bazil)
Royal Society of Canada
Chinese Academy of Sciences
Academié des Sciences (France)
Deutsche Akademie der Naturforscher Leopoldina (Germany)
Indian National Science Academy
Accademia dei Lincei (Italy)
Science Council of Japan
Russian Academy of Sciences
Royal Society (United Kingdom)
National Academy of Sciences (United States of America)
Australian Academy of Sciences
Royal Flemish Academy of Belgium for Sciences and the Arts
Caribbean Academy of Sciences
Indonesian Academy of Sciences
Royal Irish Academy
Academy of Sciences Malaysia
Academy Council of the Royal Society of New Zealand
Royal Swedish Academy of Sciences

In addition to these national academies, the following institutions specializing in climate, atmosphere, ocean, and/or earth sciences have endorsed or published the same conclusions as presented in the TAR report:

NASA’s Goddard Institute of Space Studies (GISS)
National Oceanic and Atmospheric Administration (NOAA)
National Academy of Sciences (NAS)
State of the Canadian Cryosphere (SOCC)
Environmental Protection Agency (EPA)
Royal Society of the United Kingdom (RS)
American Geophysical Union (AGU)
American Institute of Physics (AIP)
National Center for Atmospheric Research (NCAR)
American Meteorological Society (AMS)
Canadian Meteorological and Oceanographic Society (CMOS)

If this is not scientific consensus, what in the world would a consensus look like?

(Addendum: One could legitimately argue that such policy statements by necessity hide possibly legitimate internal debate while trying to present unity of position. Science is ultimately determined in peer reviewed journals. Fortunately, there is a bit of research that looked specifically at this very question — the subject of another guide entry.)

The null hypothesis says global warming is natural

Objection: Natural variability is the null hypothesis; there must be compelling evidence of an anthropogenic CO2 warming effect before we take it seriously.

Answer: The null hypothesis is a statistical test, and might be a reasonable approach if we were looking only for statistical correlation between increasing CO2 and increasing temperature. But we’re not — there are known mechanisms involved whose effects can be predicted and measured. These effects are the result of simple laws of physics, even if their interactions are quite complex.

But putting aside inappropriate application of the null hypothesis, we are indeed well outside the realm of natural global variability, as seen over the last 2,000 years and even over the last 12,000 years. We can go back several hundreds of thousands of years and we still see that the temperature swings of the glacial/interglacial cycles were an order of magnitude slower than the warming rate we are now experiencing.

In fact, outside of catastrophic geological events like the Paleocene Eocene Thermal Maximum there are no known precedents for warming this fast on a global scale. I’d say the case for “it’s all natural” is the one that needs explaining.

Oh, and by the way, we do in fact have compelling evidence.

Position statements hide debate

Objection: All those institutional position statements are fine, but by their very nature they paper over debate and obscure the variety of individual positions. The real debate is in the scientific journals.

Answer: This is a fair point. Group position statements are designed to present a united front. The best indicator of what individual scientists think is in the current scientific literature, where new and different is the paramount value and scientists are free to express their own ideas, as long as they’re supported by data and logic. What does the literature look like in terms of the climate debate? Sounds like a good topic for research.

Naomi Oreskes took on just this topic. She did an ISI database search with the keyword phrase “global climate change,” and then surveyed those resulting abstracts published between 1993 and 2003 in refereed scientific journals. There were 928.

She then divided the papers into six categories:

explicit endorsement of the consensus position,
evaluation of impacts,
mitigation proposals,
paleoclimate analysis, and
rejection of the consensus position.

The details can be read here. Oreskes’ key finding is that none of the papers fell into the last category, while 75% fell into the first three. This is a surprisingly robust consensus of opinion, especially considering that the start date was a full two years before the 1995 IPCC report, eight years before the more recent 2001 report.

A lot has happened since then, and none of it casts any doubt on the finding that the world is warming and it is primarily due to human actions.

The scientists aren’t even sure

Objection: Even the scientists don’t know that the climate is changing more than normal and if it’s our fault or not. If you read what they write it is full of “probably,” “likely,” “evidence of” and all kinds of qualifiers. If they don’t know for sure, why should we worry yet?

Answer: Probability is the language of science. There is no proof; there are no absolute certainties. Scientists are always aware that new data may overturn old theories and that human knowledge is constantly evolving. Consequently, it is viewed as unjustifiable hubris to ever claim one’s findings as unassailable.

But in general, the older and more established a given theory becomes, the less and less likely it is that any new finding will drastically change things. Even the huge revolution in physics brought on by Einstein’s theory of relativity did not render Newton’s theories of classical mechanics useless. Classical mechanics is still used all the time; it is, quite simply, good enough for most purposes.

But how well established is the greenhouse effect?

Greenhouse effect theory is over 100 years old. The first predictions of anthropogenic global warming came in 1896. Time has only strengthened and refined those groundbreaking conclusions. We now have decades of very detailed and sophisticated climate observations, and super computers crunching numbers in one second it would have taken a million 19th century scientists years with a slide rule to match. Even so, you will never ever get a purely scientific source saying “the future is certain.”

But what certainty there is about the basic issue is close enough to 100 percent that for all practical purposes it should be taken as 100 percent. Don’t wait any longer for scientific certainty; we are there. Every major institute that deals with climate-related science is saying AGW is here and real and dangerous, even though they will not remove the “very likely” and “strongly indicated” qualifiers. The translation of what the science is saying into the language of the public is this: Global warming is definitely happening and it is definitely because of human activities and it will definitely continue as long as CO2 keeps rising in the atmosphere.

The rest of the issue — how high will the temperature go, how fast will it get there, and how bad will this be — is much less certain. But no rational human being rushes headlong into an unknown when there is even a 10 percent chance of death or serious injury. Why should we demand 100 percent certainty before avoiding this danger? Science has given the human race a dire warning with all the urgency and certainty we should need to prompt action.

We don’t have time or reason to wait any longer.

Consensus is collusion

Objection: More and more, climate models share all the same assumptions — so of course they all agree! And every year, fewer scientists dare speak out against the findings of the IPCC, thanks to the pressure to conform.

Answer: The growing confluence of model results and the increasingly similar physical representations of the climate system from model to model may well look like sharing code or tweaking ’til things look alike. But it is also perfectly consistent with better and better understanding of the underlying problem, an understanding that is shared via scientific journals and research. This understanding is coming fast as we gather more and more historical and current data, all of which provides more testing material for model refinement.

Viewing the increasing agreement among climate models and climate scientists as collusion instead of consensus is a rather conspiratorial take on the normal course of scientific investigation. I suppose that fewer and fewer scientists disagreeing with the status quo is indeed consistent with some kind of widespread and insidious suppression of ideas, but you know, it is also consistent with having the right answer.

Peiser refuted Oreskes

Objection: Sure, Oreskes found no one bucking the consensus, but her paper was refuted by Benny Peiser, who did the exact same survey and found very different results.

Answer: True, Benny Peiser did attempt a similar study and submitted it as a letter to Science responding to the Oreskes study. But for very good reasons, it was not published.

Peiser claimed to find 34 articles in his “reject or doubt the consensus view” category. That’s 3 percent of the total, so even taken at face value it doesn’t cast much doubt on the consensus. But it is greater than the 0 percent Oreskes found, and serves as ammunition for the “there is no consensus” crowd.

Tim Lambert has already done an excellent dissection of Peiser’s letter here, and because Peiser was forthcoming enough to disclose the 34 abstracts in question, I encourage everyone to draw their own conclusions (they can all be seen on Tim’s blog). I will quote a few and let that speak for itself.

Benny Peiser thinks the following abstracts reject or doubt the scientific consensus on anthropogenic global warming:

(14) – The variations of global mean sea level are an important indicator of global climate change, and their measurement can provide important information for determining the socioeconomic impact of sea level change on coastal land use … [snip] … Future research will focus on establishing a realistic error budget for these measurements of global mean sea level, so that they can be put in the proper context with other observations of global climate change.
(18) – The relationship of global climate change to plant growth and the role of forests as sites of carbon sequestration have encouraged the refinement of the estimates of root biomass and production. However, tremendous controversy exists in the literature as to which is the best method to determine fine root biomass and production. This lack of consensus makes it difficult for researchers to determine which methods are most appropriate for their system … [snip] … Until the different root methods can be compared to some independently derived root biomass value obtained from total carbon budgets for systems, one root method cannot be stated to be the best and the method of choice will be determined from researcher’s personal preference, experiences, equipment, and/or finances.
(22) – The paper discusses annual to decadal climate variability and change in the European Alps by utilizing the procedure of synoptic downscaling, i.e. it investigates the influence of global to continental scale synoptic structures and processes on the regional climate of the Alps … [snip] … There is a question over whether this phenomenon is a consequence of natural climate variability or the beginning of an anthropogenic climate change.
(24) – Global climate change does not necessarily imply that temperature or precipitation is increasing at specific locations. [snip]
(25) – This paper addresses the representation of scientific uncertainty about global warming and climate change in the U.S. popular press. An examination of popular press articles about global warming from 1986 to 1995 reveals that scientific uncertainty was a salient theme. [snip]
(30) – Vegetation productivity and desertification in sub-Saharan Africa may be influenced by global climate variability attributable to the North Atlantic Oscillation (NAO) and El Nino Southern Oscillation (ENSO) … [snip] … The combined indices explained much of the interannual variability in vegetation productivity in the Sahelian zone and southern Africa, implying that both the NAO and ENSO may be useful for monitoring effects of global climate change in sub-Saharan Africa.

Those are just the ones that have no excuse whatsoever being categorized as doubting or rejecting AGW. Many others are highly questionable.

But there are a couple in his list that do indeed reject the notion of human-caused climate change. Why did Oreskes ignore those? Well, it turns out that they are editorials or letters, not peer-reviewed papers, and should not have been included except that Peiser altered the search criteria. Peiser included “all documents” in the ISI Web of Science database rather than just scientific articles, as Oreskes did, but Oreskes searched only “Sciences,” while Peiser included “Social Sciences” and “Arts & Humanities.”

If anything, Peiser’s effort strengthens Oreskes’ finding of a widespread consensus — this questionable interpretation of an inappropriate dataset was the strongest argument he was able to make.

[Update] Since this was first written, there have been a couple of developments. First, I crossed Benny Peiser’s path on the Prometheus blog. In the course of a lengthy thread under this post, I asked him directly about abstract (18) above, to which he replied, “I accept that it was a mistake to include the abstract you mentioned (and some other rather ambiguous ones) in my critique of the Oreskes essay.”

Second, it appears he has since gone even further when pressed by an Australian television program, Media Watch. The transcript is here, and Tim Lambert summarizes it here. The gist is that he has backed down to the position that just one of his 34 abstracts fit his description as rejecting the consensus view on climate change — and it was an editorial, not research of any kind.

The reason I still present this article in full, despite the backpedalling, is that as far as I can tell the retraction has been quiet and not proactive. Citations of Peiser’s “work” continue to show up all over the place.