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.

Bridging the divides

by

We often discuss the issues that arise in doing interdisciplinary work in climate science, and Liz Moyer and I have a commentary on that just out in Nature Reports Climate Change. Normally I don’t mention these kinds of pieces on the blog, but in this case the editors commissioned a nice cartoon (from Mark Roberts) illustrating our point. I liked the cartoon a lot, and so it deserves as wide an audience as possible.

A bit of context is probably useful. The three main protagonists are representative of the somewhat different foci of paleo-climatologists, climate modellers and economists. Very broadly speaking, paleo-climate science is built around the analysis of single location time series (often from holes that are drilled). Climate modellers spend a lot of time trying to see what is coming up in all its complexity, while economists tend to eschew complexity and look for insight in highly idealised situations. But in order to increase the credibility of models, they have to do well at simulating past climates and what might happen in the future is certainly informed by what has happened in the past. And in order to better understand the impacts of climate change and various proposed policies, economists will need to embrace the complexity of human-climate interactions while modellers need to better understand what aspects of climate really do make a difference. None of these things will happen if we continue to all look in different directions, and more problematically, fail to support and reward those scientists who want to bridge the divides. Sea monsters notwithstanding.

Journalistic whiplash

by

Translations: (Español)

Andy Revkin has a good article in the Science Times today on the problem of journalistic whiplash in climate change (also discussed here). This phenomena occurs with the more uncertain parts of a science that are being actively researched and where the full story is only slowly coming together. In such cases, new papers often appear in high profile journals (because they meet the ‘of general interest’ test), and are often parsed rather simplistically to see what side of the fence they fall – are they pro or anti? This leads to wide press interest, but rather shallow coverage, and leaves casual readers with ‘whiplash’ from the ‘yes it is’, ‘no it isn’t’ messages every other week.

This is a familiar pattern in health reporting (is coffee good for you/bad for you etc.), but in more recent times has started happening in climate science too. Examples picked out in the article include the hurricanes/global warming connection and the state of Greenland’s ice sheet. In both cases, many new pieces of evidence, new theories and new models are being thrown into the pot, but full syntheses of the problems remain elusive. Scientists are of course interested in knowing how it all fits together (and it usually does), but the public – unaware of what is agreed on and what is uncertain – see only the ping-pong across the media. Unlike more mature parts of the science (such as the radiative effect of greenhouse gases), there is much less context available to relate to these new pieces of science.

This spectacle of duelling and apparently contradictory science fuels the notion that scientists can’t agree on anything. Ironically, just as climate change has made it on to the front page because the weight of evidence supporting a human role in recent warming, increased coverage may actually be leading people to think that scientists are more divided on the basic questions.

Is this inevitable? Or can scientists, press officers and journal editors and journalists actually do anything about it? Your thoughts are most welcome!

Once more unto the bray

by

We are a little late to the party, but it is worth adding a few words now that our favourite amateur contrarian is at it again. As many already know, the Forum on Physics and Society (an un-peer-reviewed newsletter published by the otherwise quite sensible American Physical Society), rather surprisingly published a new paper by Monckton that tries again to show using rigorous arithmetic that IPCC is all wrong and that climate sensitivity is negligible. His latest sally, like his previous attempt, is full of the usual obfuscating sleight of hand, but to save people the time in working it out themselves, here are a few highlights.

[Read more…] about Once more unto the bray

Aerosols, Chemistry and Climate

by

Everyone can probably agree that the climate system is complex. Not only do the vagaries of weather patterns and ocean currents make it hard to see climate changes, but the variability in what are often termed the Earth System components complicates the picture enormously. These components – specifically aerosols (particulates in the air – dust, soot, sulphates, nitrates, pollen etc.) and atmospheric chemistry (ozone, methane) – are both affected by climate and affect climate, since aerosols and ozone can interact, absorb, reflect or scatter solar and thermal radiation. This makes for a rich research environment, but can befuddle the unwary.
[Read more…] about Aerosols, Chemistry and Climate

CO2 is not the only greenhouse gas, and greenhouse effects are not the only CO2 problem

by

Translations: (Español)

The title here should strike a familiar theme for most readers. Climate forcings do not just include CO2 (other greenhouse gases, aerosols, land use, the sun, the orbit and volcanoes all contribute), and the impact of human emissions often has non-climatic effects on biology and ecosystems.

[Read more…] about CO2 is not the only greenhouse gas, and greenhouse effects are not the only CO2 problem

Global trends and ENSO

by

Translations: (Español)

It’s long been known that El Niño variability affects the global mean temperature anomalies. 1998 was so warm in part because of the big El Niño event over the winter of 1997-1998 which directly warmed a large part of the Pacific, and indirectly warmed (via the large increase in water vapour) an even larger region. The opposite effect was seen with the La Niña event this last winter. Since the variability associated with these events is large compared to expected global warming trends over a short number of years, the underlying trends might be more clearly seen if the El Niño events (more generally, the El Niño – Southern Oscillation (ENSO)) were taken out of the way. There is no perfect way to do this – but there are a couple of reasonable approaches.

[Read more…] about Global trends and ENSO

North Pole notes

by

I always find it interesting as to why some stories get traction in the mainstream media and why some don’t. In online science discussions, the fate of this years summer sea ice has been the focus of a significant betting pool, a test of expert prediction skills, and a week-by-week (almost) running commentary. However, none of these efforts made it on to the Today program. Instead, a rather casual article in the Independent showed the latest thickness data and that quoted Mark Serreze as saying that the area around the North Pole had 50/50 odds of being completely ice free this summer, has taken off across the media.

[Read more…] about North Pole notes

More PR related confusion

by

It’s a familiar story: An interesting paper gets published, there is a careless throwaway line in the press release, and a whole series of misleading headlines ensues.

This week, it’s a paper on bromine- and iodine-mediated ozone loss in marine boundary layer environments (see a good commentary here). This is important for the light that it shines on tropospheric ozone chemistry (“bad ozone”) which is a contributing factor to global warming (albeit one which is about only about 20% as important as CO2). So far so good. The paper contains some calculations indicating that chemical transport models without these halogen effects overestimate ozone near the Cape Verde region by about 15% – a difference that certainly could be of some importance if it can be extrapolated across the oceans.

However, the press release contains the line

Large amounts of ozone – around 50% more than predicted by the world’s state-of-the-art climate models – are being destroyed in the lower atmosphere over the tropical Atlantic Ocean.

(my highlights). Which led directly to the headlines like Study highlights need to adjust climate models.

Why is this confusing? Because the term ‘climate models’ is interpreted very differently in the public sphere than it is in the field. For most of the public, it is ‘climate models’ that are used to project global warming into the future, or to estimate the planet’s sensitivity to CO2. Thus a statement like the one above, and the headline that came from it are interpreted to mean that the estimates of sensitivity or of future warming are now in question. Yet this is completely misleading since neither climate sensitivity nor CO2 driven future warming will be at all affected by any revisions in ozone chemistry – mainly for the reason that most climate models don’t consider ozone chemistry at all. Precisely zero of the IPCC AR4 model simulations (discussed here for instance) used an interactive ozone module in doing the projections into the future.

What the paper is discussing, and what was glossed over in the release, is that it is the next generation of models, often called “Earth System Models” (ESMs), that are starting to include atmospheric chemistry, aerosols, ozone and the like. These models may well be significantly affected by increases in marine boundary layer ozone loss, but since they have only just started to be used to simulate 20th and early 21st Century changes, it is very unclear what difference it will make at the large scale. These models are significantly more complicated than standard climate models (having dozens of extra tracers to move around, and a lot of extra coding to work through), are slower to run, and have been used much less extensively.

Climate models today are extremely flexible and configurable tools that can include all these Earth System modules (including those mentioned above, but also full carbon cycles and dynamic vegetation), but depending on the application, often don’t need to. Thus while in theory, a revision in ozone chemistry, or soil respiration or aerosol properties might impact the full ESM, it won’t affect the more basic stuff (like the sensitivity to CO2). But it seems that the “climate models will have to be adjusted” meme is just too good not to use – regardless of the context.

Of buckets and blogs

by

This last week has been an interesting one for observers of how climate change is covered in the media and online. On Wednesday an interesting paper (Thompson et al) was published in Nature, pointing to a clear artifact in the sea surface temperatures in 1945 and associating it with the changing mix of fleets and measurement techniques at the end of World War II. The mainstream media by and large got the story right – puzzling anomaly tracked down, corrections in progress after a little scientific detective work, consequences minor – even though a few headline writers got a little carried away in equating a specific dip in 1945 ocean temperatures with the more gentle 1940s-1970s cooling that is seen in the land measurements. However, some blog commentaries have gone completely overboard on the implications of this study in ways that are very revealing of their underlying biases.

The best commentary came from John Nielsen-Gammon’s new blog where he described very clearly how the uncertainties in data – both the known unknowns and unknown unknowns – get handled in practice (read that and then come back). Stoat, quite sensibly, suggested that it’s a bit early to be expressing an opinion on what it all means. But patience is not one of the blogosphere’s virtues and so there was no shortage of people extrapolating wildly to support their pet hobbyhorses. This in itself is not so unusual; despite much advice to the contrary, people (the media and bloggers) tend to weight new individual papers that make the news far more highly than the balance of evidence that really underlies assessments like the IPCC. But in this case, the addition of a little knowledge made the usual extravagances a little more scientific-looking and has given it some extra steam.
[Read more…] about Of buckets and blogs