RealClimate

Climate science from climate scientists...

You are here: Home / Archives for Climate Science

Climate Science

Incurious George

by

George Will argues now that no one would have noticed the 0.6 deg. C of global average warming to date, if the irresponsible press had not deliberately produced anxiety by pointing it out. He could be right. I expect no one would have personally noticed the ozone hole either. My grandmother smoked like a chimney and lived to be almost 100. If that nasty press had not deliberately stoked my anxieties about cigarettes and lung cancer, I would never have figured out the connection based on my personal experience. George argues that big crusading journalism is the problem. Ignorance is strength, right, George?

And, oh yeah, the global cooling stories, which appeared 30 years ago in the main-stream press (not the scientific literature). Shall we compare this with Will’s deliberate and repeated distortion of a real warning emerging from the scientific enterprise, continuing to the present day?

He looks like such an earnest man. I just don’t get it.

Significant Warming of the Antarctic Winter Troposphere

by

The “iconic” Antarctic temperature trends are the large warming seen on the Antarctic Peninsula, which has had various repercussions including the collapse of several ice shelves (some documented in a previous post). Elsewhere, though, the pattern of surface warming is more complex – trends are smaller, and while more are positive than negative they are generally not significant – see this map. Contrary to what you might have heard, this is in general agreement with model predictions.

But meanwhile, there is a record for the upper atmosphere derived from radiosondes, which we have been working on – finding old datasets and digitising them to fill in gaps. What this shows is that around East Antarctica there is a general warming of the troposphere, greatest at around mid-height (at 600 hPa) at 0.7 ºC/decade over the last 30+ years.

In itself, this is an interesting observation. The obvious question is, what does it mean? Is this natural variability; is it a response to global warming, or to changes in ozone; or something else? Ozone is unlikely, because this is winter (which conveniently means that the radiosonde temperature corrections, often a source of potential trouble, are not a problem). Two ways of trying to interpret the record are to see what GCMs run for the same period show; or to look at the re-analyses (essentially, the archived outputs from the weather-prediction models). The latter, of course, incorporate many of the radiosonde observations that we are using, and so don’t count as independant. Despite this, the ECMWF re-analyses show *greater* trends than we see in the observations; and a maximum trend over West Antarctica (which has no radisonde stations to allow us to verify this). A climate model (HadCM3, with an ensemble of four members) shows similar patterns to the observations, but this time too little warming; and a good deal of variation between the ensemble members. So neither of these is helps much with the interpretation.

So we are currently left with an open question; hopefully, this will stimulate us and other researchers to explain it in the future.

[Quick addendum: the paper itself is available via this.]

Bush on “The Fundamental Debate”

by

The President of the United States, George W. Bush, recently voiced his opinions on the science of climate change:

We — first of all, there is — the globe is warming. The fundamental debate: Is it manmade or natural. Put that aside.

The first part is the silver lining: despite receiving novelist Michael Crichton in the White House recently, Bush obviously has not bought his theory that the globe is in fact not warming. Crichton is one of the last trend sceptics who deny the warming trend is real.
[Read more…] about Bush on “The Fundamental Debate”

Another study on solar influence

by

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.

[Read more…] about Another study on solar influence

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

How much future sea level rise? More evidence from models and ice sheet observations.

by

Lots of press has been devoted to four papers in this week’s Science, on the topic of ice sheets and sea level.

We’ve already discussed the new evidence that Greenland’s glaciers are speeding up. What is new this week is an effort to evaluate the impact of future warming on Greenland by looking at what happened to it last time it got very warm — namely during the Last InterGlacial (LIG) period, about 125,000 years ago. The same group of authors looked at this in two ways, using NCAR’s Community Climate System model (CCSM) coupled to a state-of-the-art 3-D ice sheet model.
[Read more…] about How much future sea level rise? More evidence from models and ice sheet observations.

Climate sensitivity: Plus ça change…

by

Almost 30 years ago, Jule Charney made the first modern estimate of the range of climate sensitivity to a doubling of CO2. He took the average from two climate models (2ºC from Suki Manabe at GFDL, 4ºC from Jim Hansen at GISS) to get a mean of 3ºC, added half a degree on either side for the error and produced the canonical 1.5-4.5ºC range which survived unscathed even up to the IPCC TAR (2001) report. Admittedly, this was not the most sophisticated calculation ever, but individual analyses based on various approaches have not generally been able to improve substantially on this rough estimate, and indeed, have often suggested that quite high numbers (>6ºC) were difficult to completely rule out. However, a new paper in GRL this week by Annan and Hargreaves combines a number of these independent estimates to come up with the strong statement that the most likely value is about 2.9ºC with a 95% probability that the value is less than 4.5ºC. [Read more…] about Climate sensitivity: Plus ça change…

Reactions to tighter hurricane intensity/SST link

by

There was another twist to the hurricanes/global warming issue in Science Express on Friday where a new paper from the Webster/Curry team just appeared. This study, lead by Carlos Hoyos, crosses a few t’s and dots a couple of i’s on the connection of increasing numbers of intense hurricanes (Cat. 4 and 5) to sea surface temperatures (SST). Basically, they looked at a number of other key variables for hurricane intensity (like wind shear and humidity) and examined whether there was any pattern to those variables across the different ocean basins that they study. Bottom line? None of the other variables have as much explanatory power for the long term trends as SST which is the only consistently trending constituent in the mix. So far, so un-surprising. However, one interesting aspect of this story is that almost all the key players in the ongoing debate were interviewed by different journalists in various media and those comments are probably more useful for gauging the state of play than the details of the new paper itself. [Read more…] about Reactions to tighter hurricane intensity/SST link

Meteors, Nuclear Tests and Global Warming

by

What is one to make of a recent press release and submitted preprint blaming global warming on the Tunguska meteor event in 1908? Well, although it is not unknown for impact events to affect climate (the K/T boundary event springs to mind) there are a number of hurdles for any such theory to overcome before it moves into the mainstream from the wilder shores of unsubstantiated speculation.

Firstly, one would anticipate that immediate effects of the impact on climate would be strongest near the time of the impact (allowing for some inertia in the system) and decay away subsequently. Secondly, the timescales for any mechanism associated with the impact (in this case disruption of the atmopsheric water vapour) would need to be in line with the change one hopes to explain. And thirdly, one has to show that this explanation is better than the alternatives. Unfortunately, none of of these requirements are met by this hypothesis. [Read more…] about Meteors, Nuclear Tests and Global Warming

Good climate debate FAQ

by

There are a number of topics in climate science that are frequently misunderstood or mis-characterised (often by those trying to ‘scientize’ their political opinions) that come up again and again in climate-related discussions. RealClimate tries to provide context on many of these issues, and commentaries on the 1970s ‘global cooling myth‘ or whether water vapour is a feedback or a forcing are among our most referenced pieces (see our FAQ category). However, our explanations of specific points have often appeared in the middle of a larger piece, or in the comment section and are not clearly referencable. Since many of these same points keep coming up in comments and discussions, having a clear and precise resource for these explanations would be very useful and we have thought about doing just that. But it now appears that we have been beaten to the punch by a new blog run by Coby Beck, a frequent commenter here and at sci.env. His new blog ‘A few things ill-considered‘ has a point-by-point rebuttal of almost all the most common ‘contrarian’ talking points. The list of topics by category is a good place to start, and it shows the huge amount of work done so far. We’re very impressed!