RealClimate

Climate science from climate scientists...

You are here: Home / Archives for Gavin

about Gavin Schmidt

Gavin Schmidt is a climate modeler, working for NASA and with Columbia University.

The not-just-in-Copenhagen consensus

by

Anyone who spends any time mixing with climate scientists or really looking at the literature knows that the scientific consensus on the reality of human-related climate change is almost universal. Thus it is not at all surprising that methods designed to assess this consensus objectively – such as that undertaken by Oreskes in 2004 and recently re-asserted in the LA Times (non-subscription version) come up with very conclusive results. Similar studies could be done by looking at abstracts at big meetings (AGU, EGU etc.) or simply by talking to us. One could of course argue about what this means, but the existence of this consensus is not really up for debate. That doesn’t stop some people from trying of course, but these attempts have been rather embarrassing at best.

However, that didn’t prevent the latest incoherent and highly misleading press release from the Senate EPW committee being issued to support the effort. I was recently in conversation with a journalist, who told me that she’d asked the ex-talk-radio author of these EPW releases, Mark Morano, what exactly they were suppposed to achieve. Morano replied that it was to ‘get their message out’. When asked what that message was, no clear answer was forthcoming. That politicians indulge in politics is not surprising, but these releases are really scraping along the bottom. The only consolation is that they are being completely ignored by the media. Long may that consensus remain!

Medieval warmth and English wine

by

Never let it be said that we at RealClimate don’t work for our readers. Since a commenter mentioned the medieval vineyards in England, I’ve been engaged on a quixotic quest to discover the truth about the oft-cited, but seldom thought through, claim that the existence of said vineyards a thousand years ago implies that a ‘Medieval Warm Period‘ was obviously warmer than the current climate (and by implication that human-caused global warming is not occuring). This claim comes up pretty frequently, and examples come from many of the usual suspects e.g. Singer (2005), and Baliunas (in 2003). The basic idea is that i) vineyards are a good proxy for temperature, ii) there were vineyards in England in medieval times, iii) everyone knows you don’t get English wine these days, iv) therefore England was warmer back then, and v) therefore increasing greenhouse gases have no radiative effect. I’ll examine each of these propositions in turn (but I’ll admit the logic of the last step escapes me). I’ll use two principle sources, the excellent (and cheap) “Winelands of Britain” by geologist Richard C. Selley and the website of the English Wine Producers. [Read more…] about Medieval warmth and English wine

Runaway tipping points of no return

by

I wonder if any else has noticed that we appear to have crossed a threshold in the usage of the phrase ‘tipping point’ in discussions of climate? We went from a time when it was never used, to a point (of no return?) where it is used in almost 100% of articles on the subject. Someone should come up with a name for this phenomenon….

Regardless of the recent linguistic trends, the concept has been around for a long time. The idea is that in many non-linear systems (of which the climate is certainly one), a small push away from one state only has small effects at first but at some ‘tipping point’ the system can flip and go rapidly into another state. This is fundamentally tied to the existence of positive feedbacks and is sometimes related to the concept of multiple ‘attractors’ (i.e. at any time two different ‘states’ could be possible and near a transition the system can flip very quickly from one to another). Another ‘tipping point’ in non-linear systems occurs when as some parameter varies, the current attractor changes character or disappears. However it is currently being used interchangeably a number of potentially confusing ways and so I thought I’d try and make it a little clearer.

A translation into Slovak is available.
[Read more…] about Runaway tipping points of no return

Geo-engineering in vogue…

by

There was an interesting article in the NY Times this week on possible geo-engineering solutions to the global warming problem. The story revolves around a paper that Paul Crutzen (Nobel Prize winner for chemistry related to the CFC/ozone depletion link) has written about deliberately adding sulphate aerosols in the stratosphere to increase the albedo and cool the planet – analogous to the natural effects of volcanoes. The paper is being published in Climatic Change, but unusually, with a suite of commentary articles by other scientists. This is because geo-engineering solutions do not have a good pedigree and, regardless of their merit or true potential, are often seized upon by people who for various reasons do not want to reduce greenhouse gas emissions. However, these ideas keep popping up naturally since significant emission cuts continue to be seen as difficult to achieve, and so should be considered fairly. After all, if there was a cheaper way to deal with the CO2 problem, or even a way to buy time, shouldn’t we take it? [Read more…] about Geo-engineering in vogue…

Sea level in the Arctic

by

A recent conference presentation at AGU (reported here) while confirming that global sea level is indeed rising (in line with other estimates), showed that Arctic sea levels may actually be falling. On the face of it these preliminary results are a little puzzling (though note that this isn’t yet a properly peer reviewed paper, and so may not reflect what ends up in the journal), but it does reveal some of the complexities in analysing sea level in relatively small enclosed basins and so a brief overview of the different factors involved is probably useful. [Read more…] about Sea level in the Arctic

Current volcanic activity and climate?

by

There has been a lot in the news recently about current volcanic activity – Merapi in Indonesia and Bezymianny in the Kamchatka peninsula in Russia, but while most reports have focussed on the very real dangers to the local populace and air traffic, volcanoes can have important impacts on climate as well. However, there are a number of conditions that need to be fulfilled before an eruption will show up in the climate record. [Read more…] about Current volcanic activity and climate?

MY Review of Books

by

I’ve finally got round to reading a number of the many climate change-related books that have been published in recent months. These books seem to have caught the public imagination in ways that are different than in the past, and so it’s worth examining how they do. The three I’ve read are; Eugene Linden’s The Winds of Change, Elizabeth Kolbert’s Field Notes from a Catastrophe and Tim Flannery’s The Weather Makers. The first two writers are journalists, while the third is a scientist by background, and while there is some overlap in contents all of them, they are clearly distinct works in quite different styles. I’ll mostly stick to commenting on the science though… [Read more…] about MY Review of Books

How not to write a press release

by

A recent BBC radio documentary on the possible over-selling of climate change, focussed on the link between high profile papers appearing in Nature or Science, the press releases and the subsequent press coverage. One of the examples chosen was the Stainforth et al climateprediction.net paper that reported the ranges of climate sensitivity within their super-ensemble of perturbed physics runs. While there was a lot of interesting science in this paper (the new methodology, the range of results etc.) which fully justified its appearance in Nature, we were quite critical of their basic conclusion – that climate sensitivities significantly higher than the standard range (1.5 – 4.5ºC) were plausible – because there is significant other data, predominantly from paleo-climate, that pretty much rule those high numbers out (as we discussed again recently). The press coverage of the paper mostly picked up on the very high end sensitivities (up to 11ºC) and often confused the notion of an equilibirum sensitivity with an actual prediction for 2100 and this lead to some pretty way-out headlines. I think all involved would agree that this was not a big step forward in the public understanding of science.

Why did this happen? Is it because the scientists were being ‘alarmist’, or was it more related to a certain naivety in how public relations and the media work? And more importantly, what can scientists do to help ensure that media coverage is a fair reflection of their work? [Read more…] about How not to write a press release

Tropical Cyclones workshop

by

One of the nice things about a being a scientist is that you can sometimes go to workshops and meetings and actually hear something new now and again. At the well-timed Tropical Cyclones and Climate Workshop at Columbia a week or so ago, I got a chance to sit in and listen to Emanuel, Landsea, Knutson and Bell talking about their recent work, but I also got to hear some new voices (and issues) in the discussion. It was all pretty enlightening even if it didn’t end up in complete reconciliation of the different views. [Read more…] about Tropical Cyclones workshop

Pielke père et fils in Nature

by

There’s an interesting profile on Roger Pielke Jr. and Sr. in Nature this week. As readers here are probably aware, both of them have blogs (Prometheus for Jr., Climate Science for Sr.) and both have contributed to the discussions on RealClimate. Readers will also be aware that the discussions have at times been heated, though have usually remained collegial. There have been a few times when the discussion may have seemed to be at cross-purposes, but overall the exchanges have been enlightening.
[Read more…] about Pielke père et fils in Nature