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Archives for February 2006

Cloudy outlook for albedo?

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Guest Commentary by George Tselioudis (NASA GISS)

In the past few years several attempts have been made to assess changes in the Earth’s planetary albedo, and claims of global dimming and more recently brightening have been debated in journal articles and blogs alike. In a recent article entitled “Can the Earth’s Albedo and Surface Temperatures Increase Together,” that appeared in EOS, Enric Palle and co-authors use recently released cloud data from the International Satellite Cloud Climatology Project (ISCCP) to explain how it is possible for the Earth to be warming even as it’s albedo is increasing. The need for an explanation arises from the author’s claim that the earth’s albedo has increased since the year 2000, an increase that was not followed by a decrease in surface temperature. They base this claim on Earthshine data (a measurement of the glow of the dark side of the moon that they use to deduce the earth’s reflectance) and on an albedo proxy derived from ISCCP parameters after they are regressed with two years of overlapping, but not global, earthshine observations. Subsequently they claim that the rising reflectance of the Earth has not led to a reversal of global warming because the difference between low and middle-plus-high ISCCP clouds has increased in the last four years. This they say implies that as the low-level, cooling clouds have decreased during the most recent years, the high-level, warming clouds have increased even more negating any potential cloud-induced cooling.

There are several issues connected to the use of earthshine data to calculate the earth’s albedo that have been discussed in peer-reviewed publications and that I will not discuss in this posting. I will say a few things, however, about the selective use of ISCCP data in this article to construct qualitative arguments that do not stand up to detailed quantitative analysis . [Read more…] about Cloudy outlook for albedo?

Sir Nicholas Shackleton

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With the recent death of Sir Nicholas Shackleton, paleoclimatology lost one of its brightest pioneers. Over the last ~40 years, Nick made numerous far-reaching contributions to our understanding of how climates varied in the past, and through those studies, he identified factors that are critically important for climate variability in the future. His career neatly encompasses the birth of the new science of paleoceanography to its synthesis into the even newer science of ‘Earth Systems’; he made major contributions to these evolving fields throughout his life, and his insightful papers are required reading for students of paleoclimatology.
[Read more…] about Sir Nicholas Shackleton

Happy Birthday, Charles Darwin!

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Charles Darwin was born on February 12, 1809. The events commemorating Darwin’s birthday anniversary last Sunday, together with the recent conclusion of an important court case concerning the teaching of Intelligent Design (ID) in public schools prompts me to some musing concerning the relation of the Evolution/ID dialog to similar issues arising in connection with anthropogenic global warming. The age of the two theories is similar as well: Darwin introduced his theory in 1859, whereas Fourier initiated the study of the effect of atmospheres on climate with his 1821 treatise, stimulating the chain of developments leading to Arrhenius’ enunciation in 1896 of the theory that human influences on the atmosphere’s CO2 content could change the climate.

[Read more…] about Happy Birthday, Charles Darwin!

Richard Lindzen’s HoL testimony

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Prof. Richard Lindzen (MIT) is often described as the most respectable of the climate ‘sceptics’ and is frequently cited in discussions here and elsewhere. Lindzen clearly has many fundamentally important papers under his belt (work on the QBO and basic atmospheric dynamics), and a number of papers that have been much less well received by the community (the ‘Iris’ effect etc.). Last year, he gave evidence to and answered questions from, a UK House of Lords Committee investigating the economics of climate change, in which he discoursed freely on the science. I’ll try here to sort out what he said. [Read more…] about Richard Lindzen’s HoL testimony

James Lovelock’s Gloomy Vision

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James Lovelock, renegade Earth scientist and creator of the Gaia hypothesis, has written a gloomy new book called “Revenge of Gaia”, in which he argues that we should be stashing survival manuals, printed on good old-fashioned paper, in the Arctic where the last few breeding pairs of humans will likely be found after a coming climate catastrophe. The book is not published in the U.S. yet, but it is available from amazon.co.uk. Lovelock has never been one to shrink from a bold vision. What is it he sees now?

[Read more…] about James Lovelock’s Gloomy Vision

A New Take on an Old Millennium

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The subject of reconstructions of temperature variations of the past millennium has been discussed many times before on this site (see e.g. here, here, here, and here). Despite the apparent controversy, the basic conclusion–that the global and hemispheric-scale warmth of the past few decades appears anomalous in a very long-term context–has stood up remarkably well in many independent studies (see Figure 1).

Temperatures over the Past 1000 Years
Figure 1. Reconstructions of Northern Hemisphere temperatures for the last 1000 years (various colored curves) compared with instrumental record (black curve).
 [source: Wikipedia] (click to enlarge)

This is not to say that all estimates agree in their details. Indeed, there is a fair scatter among the various published estimates. [Read more…] about A New Take on an Old Millennium

An Aerosol Tour de Forcing

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Guest commentary from Ron Miller and Dorothy Koch (NASA GISS)

Scientists have confidence in a result to the extent that it can be derived by different investigators. Their confidence is increased if different techniques lead to the same conclusion. Concurrence provides evidence that the conclusion does not depend upon assumptions that occasionally are insufficiently supported. In contrast, two articles published last December on the same day arrive at very different and incompatible estimates of the effect of human-made aerosols on the radiative budget of the planet (Bellouin et al., 2005; Chung et al., 2005). They follow an earlier estimate published last year, (which included Dorothy as a co-author) that was in the middle (Yu et al., 2005). Aerosols are important to climate partly because their concentration is increased by the same industrial processes that increase the atmospheric concentration of greenhouse gases; yet aerosols generally oppose greenhouse warming. Because aerosols cause respiratory and other health problems and acid rain, they have been regulated more aggressively than greenhouse gases. Concentrations of some aerosols have decreased over the United States and Europe in recent decades as a result of environmental laws, although an increase has been observed in many thrid world regions, where economic development is a priority. In the twenty-first century, aerosol levels are anticipated to drop faster than greenhouse gases in response to future emission reductions, which will leave greenhouse warming unopposed and unmoderated.

Each published calculation of aerosol radiative forcing was a tour de force for integrating a wide variety of measurements ranging from absorption of radiation by individual particles to satellite estimates of aerosol amount. The disparate results emphasize the complexity and difficulty of the calculation. But let’s start at the beginning…. [Read more…] about An Aerosol Tour de Forcing

Wall Street Journal Again

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The Wall Street Journal has published another fair and balanced critique of climate change science and negotiations, in a Business World commentary by Holman W. Jenkins, Jr, here. A summary of the arguments is as follows:

1. It will never be possible to prove that global warming is real. In the same way, we point out, it will never be possible to prove that anybody died from lung cancer because of smoking. Did you actually witness that first DNA mutation?

2. The reasonable lay person cannot be expected to read a scientific paper, so the rational response is to ignore the issue.

3. A paper about frogs did not argue convincingly that people cause global warming.

4. People sometimes distort the truth (truly a shocking charge coming from the WSJ).

5. Global change negotiations are stalled in politics, so the science must be wrong.

Final thought: When climate does change, we’ll be able to fix it anyway.

Groundhog Day

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Living in central Pennsylvania, it would seem remiss of me not to comment on Groundhog Day today. For those not familiar with the event, Groundhog Day, which takes place on February 2 every year, is the modern American version of an age-old tradition originating in Europe centuries ago. The modern Groundhog Day is celebrated in the United States in Punksutawney Pennsylvania (about 100 miles west of Penn State University, where I teach). According to legend, if the groundhog–who is named Punxsutawney Phil–sees his shadow, there will be six more weeks of winter weather. If he does not see his shadow, there will be an early spring. After Phil emerges from his burrow on February 2, he speaks to an event official in “Groundhogese”, and his prediction is then translated for the awaiting public. The event was popularized in the 1993 movie of the same name, starring Bill Murray.

Sadly, it appears that global warming may soon add Phil to the ranks of the unemployed. With the warming of 4-8ºC (7-14ºF) predicted over North America by the end of this century if we continue to increase greenhouse gas concentrations at current rates, the answer will become simple. Spring will come early every year. While this may seem like a pleasant outcome of climate change, it could in fact lead to serious problems for plants, animals, and entire ecosystems. Living things have adapted to the timing of the seasons over many thousands of years. Here, we are changing the timing of the seasons on timescales of decades. Plants and animals just don’t adapt well to changes on such short timescales. [Read more…] about Groundhog Day