However, climate scientists are now almost immune to this kind of denialism. study released this monthThis confirms. The peer-reviewed literature was reviewed by US scientists and more than 99% of climate scientists now support the evidence for human-induced global warming.
That’s even higher than the 97% reported by an influential 2013 studyThis has been a popular statistic that is cited by both climate deniers and those who accept the evidence.
The evidence-based consensus seems to have shifted the needle even more in favor of the consensus. Or, to put it another manner, what happened to those 3% of scientists who rejected the consensus that human-caused climate change? Are we seeing a shift in the evidence over the past few decades?
Unpicking the polls
First, we need to ask if the studies are directly comparable. The answer is yes. The answer is yes. latest studyThe reexamination of literature published since 2012 was based on the same methods used by the 2013 studyHowever, there are some important refinements.
Both studies looked at the Web of Science database – an independent worldwide repository of scientific paper citations – using the keywords “global climate change” and “global warming”. However, the recent study added “climate change” to the other two keyword searches, because the authors foundMany climate-contrarian papers could not have been returned with the original terms.
The 2013 studyNearly one-third of 11,944 climate research papers were examined and found that they held a position on global warming. Out of 4,014 papers, 97% supported the consensus that humans are the cause. 1% were uncertain and 2% explicitly opposed it.
A 2015 review38 climate-contrarian papers were examined and identified various sources of bias and methodological flaws.
One of the reviewers commented that “every single one of those analyses had an error – in their assumptions, methodology, or analysis – that, when corrected, brought their results into line with the scientific consensus”.
For example, many of the contrarian papers had “cherrypicked” results that supported their conclusion, while ignoring important context and other data sources that contradicted it. Some of them ignored fundamental physics.
The 2015 reviewers also made the important point that “science is never settled and that both mainstream and contrarian papers must be subjected to sustained scrutiny”. This is the core of the scientific methodThis statement is unanimously agreed upon by most climate scientists.
Separating the natural and human influences
The Intergovernmental Panel for Climate Change has just been published. Synthesis Report, says “it is unequivocal that human influence has warmed the atmosphere, ocean and land”, and warns that the Paris Agreement goals of 1.5℃ and 2℃ above pre-industrial levels will be exceeded during this centuryWithout drastic emissions reductions
Excluding these natural variations, Earth’s surface temperature was generally stable from about 2,000 to 1,000 years ago. After that, the planet cooled by about 0.3℃ over several centuriesBefore the advent of fossil fuel-based industrialisation during the 1800s.
One study12 major volcanic eruptions were identified between 100 and 1200 CE, as compared to 17 eruptions between 1200 and 1900 CE. The general cooling that occurred before the industrial revolution was associated with increased volcanic activity in the last 800 years.
Current rates of global heating are unprecedentedIn more than 2,000 years, temperatures have risen to levels that exceed the multi-century mark. more than 100,000 years. Global average surface temperature for the decade from 2011-20 was about 1.1℃ higher than in 1850-1900. Each decade of the past four decades was warmer than any previous decade since 1850 when reliable weather observations began.
Researchers can identify natural and human factors in today’s global temperature record. This is called hindcastingIn which a climate modeling is run backwards in the time to simulate human and other natural factors. This data is then compared with the observed data in order to see which combination of factors best represents the real world.
If we remove human factors from the data set, and only include volcanic and solar factors, global average surface temperatures should have remained the same as those for the previous 100 years. But of course they haven’t.
Both the evidence and scientific consensus are now more clear than ever.