We welcome David Archer of the University of Chicago to the RealClimate team. David adds to our expertise in ocean and carbon cycle modelling and has already contributed a guest post, with more on the way. RealClimate actively solicits contributions from the wider climate science community and so if you’d like to help out, drop us a line.
Climate Science
Some recent updates
A couple of recent papers in Science this week relate to discussions we have had on RealClimate recently. The first by Curry and Mauritzen relates to the Gulf Stream Slowdown? post and describes the amount of fresh water that has been added to the North Atlantic over the last few decades (calculated from a database of salinity measurements) and what impact that has had on density and overturning circulations. There is a press release available at WHOI which is quite informative (hat tip to Joseph O’Sullivan for the link).
The second is related to the Storms and Climate Change post and is a perspective by Kevin Trenberth on the potential for a hurricanes and global warming link. The NCAR press release is available here.
These will undoubtedly not be the last word on the subject, and so we will probably be revisiting these topics at some point soon…
Betting on climate change
) (
) Guest contribution by James Annan of FRCGC/JAMSTEC.
“The more unpredictable the world, the more we rely on predictions” (Steve Rivkin). The uncertainty of an unknown future imposes costs and risks on us in many areas of life. A cereal-growing farmer risks a big financial loss if the price of grain is low at harvest time, and a livestock farmer may not be able to afford to feed his herd if the price of grain goes up. One way to reduce the risk is to hedge against it in a futures market. The two farmers can enter a forward contract, for one to deliver a set quantity of grain to the other for a fixed price at a future date. And indeed farmers do routinely use futures contracts to reduce their risks.
How much of the recent CO2 increase is due to human activities?
) Contributed by Corinne Le Quéré, University of East Anglia.
This question keeps coming back, although we know the answer very well: all of the recent CO2 increase in the atmosphere is due to human activities, in spite of the fact that both the oceans and the land biosphere respond to global warming. There is a lot of evidence to support this statement which has been explained in a previous posting here and in a letter in Physics Today . However, the most convincing arguments for scientists (based on isotopes and oxygen decreases in the atmosphere) may be hard to understand for the general public because they require a high level of scientific knowledge. I present simpler evidence of the same statement based on ocean observations, and I explain how we know that not only part of the atmospheric CO2 increase is due to human activities, but all of it.
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Gulf Stream slowdown?
) There has been an overwhelming popular demand for us to weigh in on recent reports in the Times Britain faces big chill as ocean current slows and CNN Changes in Gulf Stream could chill Europe (note the interesting shift in geographical perspective!).
Tropical Glacier Retreat
In a previous post entitled Worldwide Glacier Retreat, we highlighted the results of a study by J. Oerlemans, who compiled glacier data from around the world and used them to estimate temperature change over the last ~400 years. A question that arose in subsequent online discussion was to what extent Oerlemans had relied on glaciers from tropical regions (answer: he didn’t), and what the reasons are behind retreat of glaciers in these regions. Raymond Pierrehumbert, a climate dynamicist at the University of Chicago, kindly offered to write a guest editorial to further clarify what we do and don’t know about tropical glacier retreat. Pierrehumbert’s editorial follows below. –eric
1. INTRODUCTION
The Tropics, loosely defined as the region from 30N to 30S latitude, make up nearly half the surface area of the Earth; they are home to 70% of its people, and the vast majority of its biological diversity. Moreover, the tropical region is the “accumulation zone” for the Earth’s energy balance, with a great deal of excess solar energy being exported to help warm the rest of the planet. Detection and characterization of climate change in the Tropics is therefore a matter of great concern. Assessing the ability of climate models to reproduce this change is an important part of determining the fidelity with which the models can be expected to forecast the way climate will change in response to future increases in greenhouse gas content.
Figure 1: The Qori Kallis Glacier in the Peruvian Andes
A critique on Veizer’s Celestial Climate Driver
In a paper in Geoscience Canada, Veizer (2005) states that ‘the multitude of empirical observations favours celestial phenomena as the most important driver of terrestrial climate on most time scales‘. This paper was cited by a contributor to a debate on the website openDemocracy . In short, the argument is that the cosmic ray flux (CRF, also denoted as ‘GCR’ – galactic cosmic rays – in some papers) is the most important factor affecting our climate. Since this issue is likely to crop up from time to time, it is worth taking a closer look at the Veizer (2005) paper ( Here is a link to short summary, but the actual paper requires subscription). [Update: The actual paper is now available as supplemental material on the Geoscience Canada website.] I will try to show that CRF explanation for the recent global warming is easy to rule out.
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Global Dimming may have a brighter future
) A while ago, we wrote about Global Dimming – a reduction in downward solar radiation of about 4% or about 7W/m2 from 1961 to 1990 was found at stations worldwide. We said at the time that there were hints of a recovery underway post-1990; now research has been published showing this. From Dimming to Brightening: Decadal Changes in Solar Radiation at Earth’s Surface by Martin Wild et al. (Science 6 May 2005; 308: 847-850; subscription required for link) uses surface measurements; Do Satellites Detect Trends in Surface Solar Radiation? by Pinker et al., Science 2005 308: 850-854 uses satellites; both find a recovery of surface downward radiation since about 1990.
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“New Analysis Reproduces Graph of Late 20th Century Temperature Rise”
To our readers who have followed the supposed ‘hockey stick controversy’, this press release from NCAR just out today, will be of interest.
2005 Record Arctic Ozone Loss
You read it here first!
Update (09/05/05): Markus Rex was kind enough to send us the full figure from which Nature made their thumbnail, and which is a little clearer. He also cautions that the 2005 numbers are still preliminary, however there is a clear trend towards increasing potential for Arctic ozone loss, which is realised or not depending on the vagaries of each individual winter.