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Tuesday, 31st December 2013

Are you aware of the scientific consensus on global warming?

The Intergovernmental Panel on Climate Change (IPCC) has just announced its Fifth Assessment Report (AR5) in September 2013. This report is made available to the public on a brand-new webpage ( There, at the bottom of the webpage, are three big and conspicuous numbers: "259", "39" and "54677" (Figure 1). What do they mean?

These numbers means that AR5 is authored by 259 scientists from 39 countries around the world with 54677 comments examined. In a factsheet from the website, it was further mentioned that over 9200 scientific papers were cited in the report. From all these numbers, we can see that IPCC's AR5 is compiled based on huge amount of peer-reviewed scientific evidence, representing climate scientists' consensus on the climate change issue. One important message from AR5 is that it is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century. The certainty of human's influence on climate has increased from 90% (very likely) in the previous report published in 2007 to 95% (extremely likely) in the current report.

The above scientific consensus on the human-caused global warming is affirmed by independent surveys. Released recently in May 2013, the Consensus Project ( is one of such surveys. In this survey, researchers examined the abstracts of more than 10,000 peer-reviewed scientific papers in the last 21 years and found 97% of the papers expressing a position endorsing the human-caused global warming assessment. The researchers also directly enquired those authors who have expressed a position on global warming and found that 98% of the authors confirmed their support of the view.

As a matter of fact, more than 30 science academies, scientific organizations and research institutes around the world have clearly expressed their endorsement of human-caused global warming [1]. Then why do we hear deniers claiming the non-existence of scientific consensus every now and then? The reason is simple: if the public perceives that scientists are still arguing, they will believe that it is still an unsettled issue and play down the urgency of the situation. Lets hear one story. In early 2012, a group of "scientists" wrote on the Wall Street Journal (WSJ) claiming that there was a growing number of "scientists" disputing the fact of global warming. Five days later, some 30 climate experts rebutted on WSJ, revealing that most of the so-called "scientists" had no expertise in climate science [2].

So, in light of the above, what would you believe?

S M Lee

[1] Is there a scientific consensus on global warming?
[2] Check with climate scientists for views on climate

Figure 1.

Figure 1.      New webpage for the Fifth Assessment Report of IPCC Working Group I

Last revision date: <25 Apr 2014>