July 6, 2011

What is the scientific consensus?

Science achieves a consensus when scientists stop arguing. When a question is first asked – like ‘what would happen if we put a load more CO2 in the atmosphere?’ – there may be many hypotheses about cause and effect. Over a period of time, each idea is tested and retested – the processes of the scientific method – because all scientists know that reputation and kudos go to those who find the right answer (and everyone else becomes an irrelevant footnote in the history of science). Nearly all hypotheses will fall by the wayside during this testing period, because only one is going to answer the question properly, without leaving all kinds of odd dangling bits that don’t quite add up. Bad theories are usually rather untidy.

The testing period must eventually come to an end. Gradually, the focus of investigation narrows down to those avenues that continue to make sense, that still add up, and quite often a good theory will reveal additional answers, or make powerful predictions, that add substance to the theory. When Russian scientist Dmitri Mendeleev constructed his periodic table of elements, not only did he fit all known elements successfully, he predicted that elements we didn’t even know about would turn up later on – and they did!

So a consensus in science is different from a political one. There is no vote. Scientists just give up arguing because the sheer weight of consistent evidence is too compelling, the tide too strong to swim against any longer. Scientists change their minds on the basis of the evidence, and a consensus emerges over time. Not only do scientists stop arguing, they also start relying on each other’s work. All science depends on that which precedes it, and when one scientist builds on the work of another, he acknowledges the work of others through citations. The work that forms the foundation of climate change science is cited with great frequency by many other scientists, demonstrating that the theory is widely accepted – and relied upon.

In the scientific field of climate studies – which is informed by many different disciplines – the consensus is demonstrated by the number of scientists who have stopped arguing about what is causing climate change – and that’s nearly all of them. A survey of 3146 earth scientists asked the question “Do you think human activity is a significant contributing factor in changing mean global temperatures?” (Doran 2009). More than 90% of participants had Ph.D.s, and 7% had master’s degrees. Overall, 82% of the scientists answered yes. However, what are most interesting are responses compared to the level of expertise in climate science. Of scientists who were non-climatologists and didn’t publish research, 77% answered yes. In contrast, 97.5% of climatologists who actively publish research on climate change responded yes. As the level of active research and specialization in climate science increases, so does agreement that humans are significantly changing global temperatures.

Figure 1: Response to the survey question "Do you think human activity is a significant contributing factor in changing mean global temperatures?" (Doran 2009) General public data come from a 2008 Gallup poll.

Scientific organizations endorsing the consensus

The following scientific organizations endorse the consensus position that “most of the global warming in recent decades can be attributed to human activities”:

The Academies of Science from 19 different countries all endorse the consensus. 11 countries have signed a joint statement endorsing the consensus position:

  • 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 (USA) (12 Mar 2009 news release)

letter from 18 scientific organizations to US Congress states:

“Observations throughout the world make it clear that climate change is occurring, and rigorous scientific research demonstrates that the greenhouse gases emitted by human activities are the primary driver. These conclusions are based on multiple independent lines of evidence, and contrary assertions are inconsistent with an objective assessment of the vast body of peer-reviewed science.”

The consensus is also endorsed by a Joint statement by the Network of African Science Academies (NASAC), including the following bodies:

  • African Academy of Sciences
  • Cameroon Academy of Sciences
  • Ghana Academy of Arts and Sciences
  • Kenya National Academy of Sciences
  • Madagascar’s National Academy of Arts, Letters and Sciences
  • Nigerian Academy of Sciences
  • l’Académie des Sciences et Techniques du Sénégal
  • Uganda National Academy of Sciences
  • Academy of Science of South Africa
  • Tanzania Academy of Sciences
  • Zimbabwe Academy of Sciences
  • Zambia Academy of Sciences
  • Sudan Academy of Sciences

Two other Academies of Sciences that endorse the consensus:

This post is reproduced from Skeptical Science and is used with permission

  • Your it!

    Always ask questions… 
    For the answers are always changing.. 

  • Ian

    Since when is science about consensus? If the popular view was that Earth was flat and only one ‘flat-earth’ denier claimed the Earth was round, he would still be right in spite of the consensus. Science is about discovering the truth. Most major advances in science have been where a single scientist has challenged the consensus. The notion that there has to be be consensus in order to be right is a political concept, not a scientific one. 

  • Chris

    Exactly my thoughts Ian! Well said sir.

  • Steven

    Why is the has the Antarctic sea ice expanded since records began:
    http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seaice.anomaly.antarctic.png

  • Steve

    Bolivian President Evo Morales declared:
    “Basic services can never be privatized. They are the
    responsibility of the State. ‘Green economy’ is a new colonialism meant
    to subjugate anti-capitalist governments and nations. It [is designed]
    to colonize and privatize biodiversity at the service of a few…
    Environmentalism is an imperial strategy which quantifies every river,
    every lake and every natural product and converts it into money… By
    measuring the utility of nature in money, it colonizes nature. The
    environmentalism of capitalism is predatory colonialism… The green
    economy turns all sources of nature into a private good, at the service
    of a few.”

  • Daniel

    Because those were questions of a radically different nature. Were they not? In fact it was observable that the earth was round, and many did so – when the ships sailed into the horizon the went down, and you always saw the mast first on a ship. This is observation, a la the scientific method.

    Climatology is also an area of SCIENCE, not religious opinion such as the example you put forth. 98% of climatologists? All doing research and publishing their findings?
    Of course, it’s natural human impulse to believe whatever is the most comfortable for you, that we’re not destroying the environment. It is 100% irrefutable that we’re destroying it. Have you looked outside? Seen the deforestation and gigantic amounts of pollution to the atmosphere? Of course we are.

  • Gary

    In 2006 I went to Turkey and looked at some ruins there. The ruins were of Roman origin, one showed Emperor Hadrian with his foot on a globe of the earth. It was accepted knowledge that the Earth was round, the flat earth concept emerged later from the religious teachings.
    I do not think there was a real scientist who thought that the world was flat, and certainly any form of observation would prove the obvious just as climate change has real basis in science the only doubt was how to handle the situation and how serious was the problem, as we are learning today the problem is very serious but quantifying it is a problem remains to be done better.