What We Knew in ’81

April 9, 2012

A lot of people really appreciated getting a look at Mike MacCracken’s 1982 (above) lecture at Sandia Labs, which gave a comprehensive overview of what was then known about climate change. Quite a lot, it turns out.(if you’ve seen it, keep going. if not, watch now. I’ll wait)

RealClimate has just posted a reminder of a similar compilation a year earlier, James Hansen’s 1981 Science piece.

RealClimate:

Sometimes it helps to take a step back from the everyday pressures of research (falling ill helps). It was in this way we stumbled across Hansen et al (1981) (pdf). In 1981 the first author of this post was in his first year at university and the other just entered the KNMI after finishing his masters. Global warming was not yet an issue at the KNMI where the focus was much more on climate variability, which explains why the article of Hansen et al. was unnoticed at that time by the second author. It turns out to be a very interesting read.

They got 10 pages in Science, which is a lot, but in it they cover radiation balance, 1D and 3D modelling, climate sensitivity, the main feedbacks (water vapour, lapse rate, clouds, ice- and vegetation albedo); solar and volcanic forcing; the uncertainties of aerosol forcings; and ocean heat uptake. Obviously climate science was a mature field even then: the concepts and conclusions have not changed all that much. Hansen et al clearly indicate what was well known (all of which still stands today) and what was uncertain.

Next they attribute global mean temperature trend 1880-1980 to CO2, volcanic and solar forcing. Most interestingly, Fig.6 (below) gives a projection for the global mean temperature up to 2100. At a time when the northern hemisphere was cooling and the global mean temperature still below the values of the early 1940s, they confidently predicted a rise in temperature due to increasing CO2 emissions. They assume that no action will be taken before the global warming signal will be significant in the late 1990s, so the different energy-use scenarios only start diverging after that.

The first 31 years of this projection are thus relatively well-defined and can now be compared to the observations. We used the GISS Land-Ocean Index that uses SST over the oceans (the original one interpolated from island stations) and overlaid the graph from the KNMI Climate Explorer on the lower left-hand corner of their Fig.6.

Given the many uncertainties at the time, notably the role of aerosols, the agreement is very good indeed. They only underestimated the observed trend by about 30%, similar or better in magnitude than the CMIP5 models over the same period (although these tend to overestimate the trend, still mainly due to problems related to aerosols).

To conclude, a projection from 1981 for rising temperatures in a major science journal, at a time that the temperature rise was not yet obvious in the observations, has been found to agree well with the observations since then, underestimating the observed trend by about 30%, and easily beating naive predictions of no-change or a linear continuation of trends. It is also a nice example of a statement based on theory that could be falsified and up to now has withstood the test. The “global warming hypothesis” has been developed according to the principles of sound science.

References

  1.  J. Hansen, D. Johnson, A. Lacis, S. Lebedeff, P. Lee, D. Rind, and G. Russell, “Climate Impact of Increasing Atmospheric Carbon Dioxide”, Science, vol. 213, 1981, pp. 957-966.DOI.
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8 Responses to “What We Knew in ’81”

  1. ahaveland Says:

    Peter, an excellent presentation as usual – but one suggestion:
    I realise that videos can’t (yet) be updated once uploaded to youtube, but in future, linger for a few more seconds at 9:05, to allow the magnitude of the shocking difference between the projection and observation of arctic melt to sink in.


  2. [...] What We Knew in ’81 (climatecrocks.com) Share this:EmailLinkedInFacebookTwitterStumbleUponRedditDiggPrintLike this:LikeBe the first to like this post. This entry was posted in Global Warming & Climate Change, My Opinion, Susutainable Buildings & Climate Initiatives and tagged Environmental impact assessment, Global Environment Outlook, Global Warming, India, UNEP, United Nations, United Nations Environment Programme, United Nations General Assembly. Bookmark the permalink. ← Bangkok floods – Next, New Delhi ? Will UNFCCC survive the fall of EU in Rio+20 ? → [...]


  3. Great video.

    As I said on the Real Climate site it was a bit of a coincidence that it did a post so soon after I looked at the 1981 paper in my own blog, ‘What Hansen et al got right decades ago’.

    http://reallysciency.blogspot.co.uk/2012/03/what-hansen-et-al-got-right-decades-ago.html


  4. [...] predicted more than 30 years ago). Here’s an excerpt of an article from Peter Sinclair at climatecrocks.com: “A lot of people really appreciated getting a look at Mike MacCracken’s 1982 (above) [...]

  5. neilrieck Says:

    Peter, this is your best presentation to date. Keep up the good work.


  6. [...] What We Knew in ’81 « Climate Denial Crock of the Week. Share this:TwitterFacebookLike this:LikeBe the first to like this post. [...]


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