Posts by Carla Wise

The IPCC 4th Assessment Report

On February 2, the IPCC, an international group of scientists charged with reviewing the evidence on global climate change, issued “Climate Change 2007: The Physical Science Basis,” a summary for policymakers. The summary describes progress in understanding the human and natural drivers of climate change. The report is available for download at http://www.ipcc.ch/.

As has been widely reported, the new report states clearly that the earth’s climate is changing, and it attributes the bulk of these changes to human activities. Specifically, the IPCC report states that warming is “unequivocal,’ humans are “very likely” responsible (defined as more than 90% probability) and the earth’s climate is “very unlikely” to be so insensitive as to render future warming inconsequential.

The latest report from the IPCC is important for several reasons. First, it represents a consensus of scientists from around the world on the state of the science. Six-hundred authors nominated by 40 countries contributed, and representatives from 113 countries gathered to review the final draft before its release. Thus it represents an extraordinary agreement among the top climate scientists in the world on the certainty and seriousness of human-caused global climate change.

Second, this report highlights the amount and quality of new scientific evidence on the size, causes, and growing impacts of climate change. The last IPCC report, issued in early 2001, was full of uncertainties about the likelihood that human activities were behind most of the warming, and potential future warming. Here is what John Holdren, president of the AAAS, says in reflecting on the 2007 assessment: “…since 2001 there has been a torrent of new scientific evidence on the magnitude, human origins, and growing impacts of climatic changes that are underway. In overwhelming proportions, this evidence has been in the direction of showing faster change, more danger, and greater confidence about the dominant role of carbon dioxide from fossil-fuel burning and tropical deforestation in causing the changes that are being observed.”

Finally, the IPCC Fourth Assessment Report seems to be adding strength to a growing movement among scientists and others to call for immediate and serious action to begin to tackle the growing climate crisis. On February 18, the board of the AAAS issued a consensus statement declaring global climate change a growing threat to society, and calling for immediate action to rapidly reduce greenhouse gas emissions; see http://www.aaas.org/news/releases/2007/0218am_statement.shtml
AAAS president John Holdren issued a compelling argument as well: Read the full statement.

Other News

Here’s one other interesting item from the Feb 2 issue of Science magazine:
Trying to predict ecological responses to climate change may be trickier than previously thought: The summary below describes a paper published in the Feb 2, 2007 issue of Science magazine.
Most forecasts of ecological responses to climate change assume that these can be based on individual species tolerances for changing moisture or temperature regimes. Suttle et al. (p. 640; see the Perspective by Walther) challenge this assumption. In a 5-year experiment, they examined the consequences of alternative climate change scenarios in a grassland ecosystem in California, USA. Manipulation of rainfall over replicated 10-m diameter plots showed that higher-order species interactions dictate responses throughout the community. The effects on plant and arthropod abundance and diversity were the reverse of what would have been predicted based on individual species responses. Click here for article abstract.

January Climate Science News
By Carla Wise

Climate change and tree planting

Tree planting is an increasingly popular activity associated with “carbon offsetting“ projects people and businesses are buying to try to neutralize their carbon emissions. However, recent studies suggest that planting trees outside the tropics may not help slow climate change. Dr. G. Bala, Dr. K. Caldeira, and others used a computer model to determine the impact forests in different parts of the world would have on temperature. The analysis found that forests in tropical regions cool the planet by sequestering carbon dioxide and by increasing evaporation, which increases cloud cover. However, forests planted in other latitudes may have neutral or even harmful effects on climate change. This is because while these forests absorb carbon, they also tend to be darker than fields or farms they replace. Darker vegetation absorbs more sunlight, holding more heat near ground level. This effect is most pronounced in snowy areas, where planting trees may actually have an overall warming effect.

See the following articles for more details on this work:

http://www.treehugger.com/files/2006/12/planting_trees.php

http://www.sacbee.com/110/story/108542.html

http://www.sciencedaily.com/releases/2005/12/051206162547.htm

Polar bears and melting ice

The US Fish and Wildlife Service agreed in January to decide whether to list the polar bear as threatened under the Endangered Species Act (ESA). Citing warming temperatures that are melting the sea ice on which polar bears depend, the agency has said it will decide within a year whether listing is warranted. The announcement came after several environmental groups took the agency to court for failure to respond to requests to give the polar bear protection under the ESA.

There is growing evidence that polar bear habitat (sea ice) is declining quickly with a rapidly warming arctic. There is also evidence from some polar bear populations of declining numbers, fewer offspring, and thinner bears.

For more information, see:

http://www.gainesvilletimes.com/news/stories/20070122/localnews/151449.shtml

http://www.cbsnews.com/stories/2007/01/23/ap/tech/mainD8MR9OMG2.shtml

http://www.sciencemag.org/cgi/content/full/315/5808/25?etoc

By Carla Wise

In December, a number of climate science papers were published on topics including melting sea ice, phytoplankton dynamics, and underwater deposits of frozen methane. It is difficult to choose which to highlight, so I just picked two that I found interesting.

Prairie grass mixture holds great promise for biofuel production

A key element to reducing the threat of very large, destructive climate change is developing alternative fuels for transportation. Until now, biofuels have been produced primarily from monocultures of corn or soybeans grown on fertile soils. These biofuels are “carbon-positive” because their production and combustion increases atmospheric CO2, although not as much as do fossil fuels. In addition, the use of good farmland to grow crops for biofuels sets up potential conflict between land use for fuel and food.
A new study led by David Tilman shows that growing diverse mixtures of prairie plants has the potential to provide more usable energy per acre than corn grain ethanol or soybean biodiesel and is far better for the environment. Tilman’s work shows that the use of 16-species mixtures of native prairie plants grown and used for biofuel could be “carbon negative,” meaning that they would actually subtract carbon dioxide from the atmosphere. His team also demonstrated that the polycultures can be grown successfully with low inputs, without fertilizer and on degraded, infertile soils.
Biofuel production has gained attention in recent years as a potential solution to climate change, diminishing oil reserves, and energy security. However, using food-based biofuels creates many problems. Tilman et al. state: “Current biofuel production competes for fertile land with food production, increases pollution from fertilizers and pesticides, and threatens biodiversity when natural lands are converted to biofuel production.” This work is a real breakthrough, because it demonstrates that biofuels produced by polycultures of prairie species can be “carbon negative” and may provide a substantial portion of global energy needs in a sustainable and environmentally beneficial manner without competing with food production for fertile lands.

The findings are published in the Dec. 8, 2006 issue of the journal Science and featured on the cover. (http://www.sciencemag.org/cgi/content/short/314/5805/1598)

Subscribers can read the full article at:
http://www.sciencemag.org/cgi/reprint/314/5805/1598.pdf

Monsoon intensity increases with climate change

The monsoon is the great life-giver and the great destroyer of the Indian subcontinent. Crops, animals, and food for half of the world’s population depend on rain from these annual storms. But when the storms are too intense, crops are inundated, animals drown, and floods and diseases cause great human suffering. As global climate change has been occurring, the stability of the Indian monsoon rainfall has been a puzzle.
The overall level of rainfall has changed little over the past century. But researchers have discovered a trend within the annual measurements of fewer but more extreme monsoon rains with warming global temperatures. B.N. Goswami and colleagues studied rain gauge data from stations throughout India from 1951 to 2000. They found that with warming temperatures, there has been a trend of fewer but more extreme monsoon rains. Light rain events have declined significantly while heavy and very heavy rain events have increased, keeping the annual mean rainfall essentially unchanged. This study suggests that the impact of continued warming will be to increase flooding and related hazards in central India in the coming decades. The implications of these findings are quite serious and potentially devastating for the many people of the Indian subcontinent.

The findings are published in the Dec.1, 2006 issue of Science:
http://www.sciencemag.org/cgi/content/abstract/314/5804/1442

Subscribers can read the full article at:
http://www.sciencemag.org/cgi/reprint/314/5804/1442.pdf

Introduction:

This addition to the YPCC web site is my effort to provide a resource for those interested in climate change who do not read the scientific literature on climate change. Each month I will summarize my picks of the highlights of climate change science news. I believe it is critical to keep up with the exploding field of climate science to work toward solutions. While this effort innevitably cannot cover all the new scientific evidence coming out, I hope it will still be a useful resource. I welcome feedback.

Background

Three decades of intensive scientific study, hundreds of peer-reviewed journal articles, countless studies, scores of devoted scientists, and untold hours of work have been expended quantifying and understanding global climate change. The vast majority of climatologists now agree that global climate change is underway, and that human activities are the largest contributor. As scientists have learned more, the seriousness and urgency of the threat of global warming has deepened, and current impacts have been measured worldwide. Many scientists and others argue that the time for responding to “climate skeptics” is over. I agree.

It is well known that human activities have caused the more than 30% rise in atmospheric CO2 and other greenhouse gases in the past few centuries, and that this rise is the largest contributor to the climate warming over the past century. There is still debate about the amount and speed that the temperature will rise in the future, due to the complexity of understanding and modeling all the elements that affect climate, but it in no way undermines the validity of the general conclusions.

Those of us working on climate change need to understand current science and be able to communicate about the essential elements of scientific knowledge on climate change. The difficulty is that climate researchers are constantly expanding and refining their understanding of human impacts on global climate.

Climate Science News Highlights - November, 2006

How fast are the ice sheets melting?
Scientists have been discussing and measuring ice sheet melting, particularly at the poles, in recent years. It has far-reaching implications for polar species, and global implications for large and rapid sea level rise. Greenland contains about 10% of global ice mass, and complete melting would raise global sea level by about 6.5 meters. Several recent studies have suggested that Greenland ice melting has accelerated dramatically since 2003. In November, in a study using new analysis techniques, Lutchke et al. confirmed that Greenland ice is melting at an accelerating rate, but suggested the rate may not be as fast as recently suggested in a September paper by Chen et al.. Cazenave (Perspective) discusses some of the reasons for the discrepancies, and calls for more research to improve estimates of ice loss in Greenland and Antarctica.

The take home message is that global warming is melting polar ice sheets, and Greenland ice is now melting at an alarming rate. Remote-sensing data and models have been employed in different ways in each of the studies, resulting in differing results. The Lutchke team found that the Greenland ice sheet has lost about 100 gigatons of ice per year between 2003 and 2005, as compared to the average ice loss rate of about 12 Gt of ice per year for the decade between 1992 and 2002. However, this estimate is much less than other recent rate calculations, which are closer to 240 Gt of ice per year for the same period. Uncertainty remains about the speed of Greenland ice loss.

Species are moving, adapting, and dying due to global warming.
As a conservation biologist, I have been aware for some time of research measuring signals from plants and animals reacting to a warming climate. Entire ecosystems have started to shift, and biologists have been out there quietly, painstakingly documenting the changes. A second major scientific story about global climate change came out in the Annual Review of Ecology, Evolution, and Systematics in November. In her paper, “Ecological and Evolutionary Responses to Recent Climate Change,” Camille Parmesan reviews the recent scientific literature quantifying the effects of global warming on living things. She reviews 866 studies, and finds evidence that climate change has affected species worldwide, in all taxonomic groups and all ecosystems. Other studies have described specific problems faced by species, populations, or areas affected by climate change, but this is the first comprehensive analysis of the planet-wide impacts of global warming on living things.

It is hard to overstate the scope of the impacts she documents. This review describes ecological changes in phenology and distribution of plants and animals in all well-studied marine, freshwater, and terrestrial groups. These observed changes are heavily biased in the directions predicted from global warming and have been linked to local or regional climate change through correlations between climate and biological variation, field and laboratory experiments, and physiological research. The most negatively affected groups include range-restricted species, particularly polar and mountaintop species, tropical coral reef organisms, and amphibians. Impacts include changes in predator-prey and plant-insect interactions, evolutionary adaptations to warmer conditions, observed genetic shifts, and extinction of entire species.

For a pdf of the full article, go to:
http://cns.utexas.edu/communications/File/AnnRev_CCimpacts2006.pdf