In an earlier post, we discussed a review article by Frohlich et al. on solar activity and its relationship with our climate. We thought that paper was quite sound. This September saw a new article in the Geophysical Research Letters with the title «Phenomenological solar signature in 400 years of reconstructed Northern Hemisphere temperature record» by Scafetta & West (henceforth referred to as SW). This article has now been cited by US Senator James Inhofe in a senate hearing that took place on 25 September 2006 . SW find that solar forcing accounts for ~50% of 20C warming, but this conclusion relies on some rather primitive correlations and is sensitive to assumptions (see recent post by Gavin on attribution). We said before that peer review is a necessary but not sufficient condition. So what wrong with it…?
Short and simple arguments for why climate can be predicted
Sometimes, I encounter arguments suggesting that since we cannot predict the weather beyond a couple of weeks, then it must be impossible to predict the climate in 100 years. Such statements tend to present themselves as a kind of revelation, often in social settings and parties after I have revealed for some of the guests that I’m a climatologist (if I say I work for the Meteorological Institute, I almost always get the question “so, what’s the weather going to be like tomorrow?”). Such occasions also tend to be times when I’m not too inclined to indulge in deep scientific or technical explanations. Or when talking to a journalist who wants an easy answer. In those cases I try to provide a short and simple, but convincing, explanation that is easy for most people to understand why climate can be predicted despite the chaotic nature of the weather (a more theoretical discussion is provided in the earlier post Chaos and Climate). One approach is to try to relate the topic to something with which they are familiar, such as to point to empirical observations which most accept (I suppose with hindsight it could be similar to the researchers in the early 20th century trying to convince that nuclear reactions were possible – just look at the Sun, and there is the proof! Or before that, the debate about whether atoms were real or not – just look at the blue sky, and you look at the proof…). I like to emphasised the words ‘weather‘ and ‘climate‘ above, because they mean different things.
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The Copenhagen Consensus
In a Wall Street Journal (WSJ) editorial published July 8, K.A. Strassel reports on a new and recent ‘Copenhagen Consensus‘ (CC) meeting in Georgetown, arranged by Bjørn Lomborg, a controversial Danish public figure. I personally find the name ‘The Copenhagen Consensus’ a misnomer because it does not reflect what it is all about – I think that ‘The Lomborg exercise’ would be a more appropriate name. The WSJ article and the Lomborg meeting do not involve much science in my opinion, but are mere political exercises. However, since the CC, Lomborg, and the WSJ editorial in my opinion employ rhetorical means for downplaying the importance of climate change, the story warrants a comment on the RC forum. I will try to expose the poorly hidden communication concerning the climate change. Thus, the focus of this post is on the communication concerning climate change as well as the logic behind the arguments.
Communicating Science & Technology
I recently attented a conference on communicating science and technology in Tromsø, Norway June 6-9 (CST060606). The conference was filmed and the presentations can be viewed over the internet broadcast. There were many very good presentations bringing up important points, and one by Lawrence Krauss (Science under Attack) should not be missed. Also, the presentation by the nobel laurate Ivar Giaever provides a lot of food for thought, and Janet Sumner told how the science can be ‘jazzed up’ and made more accesible on the BBC (touching onto the climate science – climate chaos season – and showing clips of ‘Rough science’, ‘Labrats’ and ‘Science Shack’, in association with the Open University). The conference was attended by scientists, teachers, politicians, and people from the media. The topics of presentations span issues such as climate, ID, media, schools, and politics (the Norwegian minister of education). [I also gave a fairly diasterous :-( presentation on communicating climate with reference to RealClimate.org :-).]
Lessons from Venus
by Rasmus Benestad and Ray Pierrehumbert
A special report in The Observer on Sunday (April 9) titled ‘Venus – The Hot Spot’, provides a well-written account on a mission called the Venus Express. The Venus express is an European Space Agency (ESA) mission to probe the the atmosphere of Venus and address questions regarding the differences between the climates on Venus and Earth. According to the plans, the probe will enter the final orbit around Venus in May 2006, i.e. within about a month.
What relevance does a mission to Venus have for a blog like RealClimate? Primarily, Venus offers scientists the chance to see how the same basic physics used to study Earth’s climate operates under a very different set of circumstances. In one sense, Venus is rather similar to Earth: it has nearly the same mass as Earth, and while its orbit is somewhat closer to the Sun, that effect is more than made up for by the sunlight reflected from Venus’ thick cloud cover. Because of the cloud cover, the surface temperature of Venus would be a chilly -42C if were not for the greenhouse effect of its atmosphere. In reality, the surface of Venus, at 740K (467C) is even hotter than the surface of Mercury, which is a (relatively!) pleasant 440K. Per unit of surface area, the atmosphere of Venus has as much mass as about 100 Earth atmospheres, and it is almost pure CO2. This accounts for its very strong greenhouse effect. In contrast, the CO2 in the Earth’s atmosphere accounts for a mere .00056 of the full mass of one Earth atmosphere.
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Another study on solar influence
In a recent paper in Geophysical Research Letters, Scafetta & West (S&W) estimate that as much as 25-35% of the global warming in the 1980-2000 period can be attributed changes in the solar output. They used some crude estimates of ‘climate sensitivity’ and estimates of Total Solar Irradiance (TSI) to calculate temperature signal (in form of anomalies). They also argue that their estimate, which is based on statistical models only, has a major advantage over physically based considerations (theoretical models), because the latter would require a perfect knowledge about the underlying physical and chemical mechanisms.
The Greenland Ice
by Rasmus Benestad, Eric Steig and Gavin Schmidt
In a recent paper in Science, Eric Rignot and Pannir Kanagaratnam present new satellite observations of the speed of glaciers of Greenland, and find that they are sliding towards the sea almost twice as fast as previously thought. Additionally, between 1996 and 2005, they detected a widespread glacier acceleration and consequently an increased rate of ice discharge from the Greenland ice sheet. However, previous papers have recently noted an increase in snow accumulation in the interior (i.e. Johannessen et al., 2005), so how do these different measurements fit into the larger picture of Greenland’s net mass balance?
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Was the record Amazon drought caused by warm seas?
On December 11, 2005, The New York Times ran a story on record drought conditions in the Amazonas region of Brasil, linking it to global warming, and specifically the warm ocean temperatures in the North Atlantic that have also been linked to the ferocity of the 2005 Atlantic hurricane season. This prompted a response from Chris Mooney, calling for a comment from RealClimate about whether such an assertion is valid, as we earlier made it very clear that it is impossible to say whether one single extreme event in a very noisy environment – such as Hurricane Katrina – is related to climate change. So we decided to take a look at this phenomena, and address why there might be a connection and what it takes to make an attribution. [Read more…] about Was the record Amazon drought caused by warm seas?
Naturally trendy?
From time to time, there is discussion about whether the recent warming trend is due just to chance. We have heard arguments that so-called ‘random walk‘ can produce similar hikes in temperature (any reason why the global mean temperature should behave like the displacement of a molecule in Brownian motion?). The latest in this category of discussions was provided by Cohn and Lins (2005), who in essence pitch statistics against physics. They observe that tests for trends are sensitive to the expectations, or the choice of the null-hypothesis .
Greenhouse gases help seasonal predictions
) The conventional wisdom in meteorology has been that certain factors such as the complete oceanic state and the exact concentrations of greenhouse gases are of minor importance for a normal weather forecast. Moreover, whereas sea surface temperatures (SST) are important, the deep sea temperatures are believed to have little impact for predictions for the next few days. The reason is that the ocean reacts slowly to changes in the atmosphere (has much higher inertia and much higher heat capacity). Hence, the most important information needed for such a weather forecast is the atmospheric initial conditions, a description of what the atmosphere and the SST look like when the weather model starts computing the weather evolution.
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