How certain is the scientific community?
Aren’t there good points and peer-reviewed research on both sides of a climate change “debate?” If the debate is, “Is it happening and is it predominantly human-caused?”, then NO there is not any significant scientific debate, not anymore. While you can find web pages and organizations that claim the issue is still up for debate and claim that there is no scientific consensus, they do not rely on peer-reviewed research or valid measures. For more on this see the section on CLIMATE DENIAL AND U.S. POLICY.
Who should we rely on to gain an understanding of the science of climate change? Climate scientists. Not just any “scientist” but one that has training and specialization in that which they are making claims about. Should we ask a geologist about the impact of carbon dioxide emission on the hunting range of polar bears? Should we ask a zoologist about how the increased methane concentrations in the atmosphere impact solar radiation? No. However, it is not even a question of “who” but rather “what?” It is not the scientists themselves that we should rely on, rather it is their peer-reviewed research. There are thousands of peer-reviewed articles and books that contribute specific aspects of the collective understanding of anthropogenic climate change. I have linked to a few of them throughout this section but I largely rely on expert summaries and compilations of the research. Organizations like the Intergovernmental Panel on Climate Change (IPCC), NASA, the National Oceanic and Atmospheric Administration (NOAA), and the National Academy of Sciences are some key examples of expert-led organizations that generate original research and authoritative overviews of the science.
In a 2020 overview of the science, the National Academy of Sciences in the US and the Royal Society in the UK stated: “The evidence is clear. However, due to the nature of science, not every detail is ever totally settled or certain. Nor has every pertinent question yet been answered. Scientific evidence continues to be gathered around the world. Some things have become clearer and new insights have emerged.”
When scientists conduct research they often state levels of confidence or certainty that their findings are not statistical anomalies or simply occurred by chance. The realities of the natural and social world are immensely complex. Scientists must design their research to account for likely possibilities based on informed hypotheses (formed from the knowledge of the canon of existing research). Analysis in the field or a lab can test the influence of different variables but there is always some degree of uncertainty. This is part of what makes science more rigorous than other forms of inquiry. (For more on why we should believe science, review this section.) However, as more and more research tests different possibilities and points to similar outcomes, the scientific community becomes increasingly confident in their certainty.
In the 2014 Fifth Assessment report by the panels of scientists assembled for the IPCC, they reported their levels of certainty in the following ways:
Is the planet warming? UNEQUIVOCALLY and in many unprecedented ways.
Is this warming due to human activity? EXTREMELY LIKELY. This is an “increase” from “very likely” expressed in the 2007 IPCC report.
They add some details here that demonstrate the specific areas of research and their current levels of confidence. “The evidence for human influence on the climate system has grown since the IPCC Fourth Assessment Report (AR4). It is extremely likely that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in GHG concentrations and other anthropogenic forcings together. The best estimate of the human-induced contribution to warming is similar to the observed warming over this period. Anthropogenic forcings have likely made a substantial contribution to surface temperature increases since the mid-20th century over every continental region except Antarctica. Anthropogenic influences have likely affected the global water cycle since 1960 and contributed to the retreat of glaciers since the 1960s and to the increased surface melting of the Greenland ice sheet since 1993. Anthropogenic influences have very likely contributed to Arctic sea-ice loss since 1979 and have very likely made a substantial contribution to increases in global upper ocean heat content (0–700 m) and to global mean sea level rise observed since the 1970s.”
Have IPCC Assessment Reports ever gotten it wrong? Yes. In fact, much of their early projects have been found to be UNDER-estimates of the level of emissions, the average temperature increase, Arctic ice melting, and more. See here. Other scientists argue that the IPCC process produces reports that are too conservative in their estimates. Also, see debates here and here.
The IPCC’s Sixth Assessment Report is due out in 2021.