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Northern peatlands, typical for subarctic Scandinavia and Russia, contain one third of the world’s soil organic carbon. How much extra carbon these soils will release to the atmosphere, through accelerated respiration in a warmer climate, has been pretty much guesswork. Data from an eight-year in situ experiment carried out in Sweden now suggest that even modest warming will release enough extra carbon to effectively equalize the European Union’s emissions reductions achieved under the Kyoto Protocol.

Ellen Dorrepaal and her colleagues studied ecosystem response to climate warming at a test site near the Swedish Abisko scientific research station, some 200 kilometres inside the Arctic Circle. In a paper in Nature today (subscription required) they report that warming accelerated the respiration of carbon in peat overlaying the permafrost by almost 70 % - much more than previously thought. Here's an editor's summary.

Extrapolated to the total northern peatland area, the results suggest that climate warming of 1 degree Celsius over the next decade might lead to a global increase in respiration of 38-100 million tonnes of carbon per year. For comparison: The EU’s Kyoto target is to reduce emissions by 92 million tonnes of carbon per year.

The researchers stress that the effect is likely to last: “In contrast to long-term studies in forest, meadow and tundra ecosystems, the warming effect did not decline towards the eighth year of the study,” they write.

The net effect of warming on northern carbon reservoirs includes possible gains from increased plant growth. But in Arctic ecosystems dominated by peat and moss, there are too few productive woody shrubs growing to offset the warming effect on soils.

Quirin Schiermeier

Image: Subarctic peatland in Abisko, North Sweden where the consequences for CO2-respiration rates were investigated. Credit: Ellen Dorrepaal

Posted by Quirin Schiermeier on July 30, 2009
Categories: Categories, Biosphere feedbacks, Climate Science, GHG emissions, Quirin Schiermeier, Topics, Uncertainty | Permalink | Comments (3) | TrackBacks (0)

Uncertainty in regional climate projections isn’t going away, and that’s an inconvenient truth the development community will have to face, says Christoph Müller of the Potsdam Institute for Climate Impacts Research in Germany.

Müller recently authored a report on expected climate change impacts in sub-Saharan Africa, at the behest of the German Development Institute (GDI), a Bonn-based think tank. A top recommendation of the final report, published 24 April and presented at the IHDP conference last month, is that adaptation strategies should not be motivated by specific impact projections, but instead should work on reducing vulnerability to environmental change in general.

An expert on climate impacts on agriculture and land-use, Müller found while scoping the report for GDI that there was a mistaken assumption by development experts that many of the current uncertainties in predicting climate change will soon clear up. “In the adaptation community, they often have the feeling that if we wait for another five years, we will know exactly what the weather will be,” he says.

So he turned the focus of the report around from cataloging impacts to dealing with uncertainty. “This report basically is trying to raise awareness that you will never get very accurate projections of what you will have to adapt to. Don’t wait for that. You have to adapt to uncertainty,” says Müller.

I talked to Müller to find out more about what adaptation planners in sub-Saharan Africa are up against and how they might tackle changes they can't forsee. What climate models agree on is that the continent will warm a bit more than the global average - roughly 2.0 to 4.5 degrees centigrade, according to three emissions scenarios of the Intergovernmental Panel on Climate Change.

“But that’s where the certainty stops,” he says. Precipitation projections, for example, are important for many impacts studies - of freshwater availability, agricultural production, and development of water-hungry industries - but global climate models differ wildly on precipitation in African locales. “There’s maybe only a few locations in sub-Saharan Africa where you don’t have a scenario that says it’s going to get significantly wetter and another scenario that says it’s going to get significantly drier,” Müller points out.

A particular problem for sub-Saharan Africa is that observational data from meteorological stations is sparse, and many stations formerly sending out data have stopped ('historical' stations on map, below) - making it hard to produce local projections. This is usually achieved through a technique called ‘downscaling’, which involves using weather statistics and interpolating data to add details between the distant grid points of a global climate model. But without recent observations to constrain the calculations, it becomes near impossible to fill in this extra information with any degree of accuracy.

Continue reading "Development community must accept uncertainty" »

Posted by Anna Barnett on May 27, 2009
Categories: Adaptation, Anna Barnett, Society, Uncertainty | Permalink | Comments (0) | TrackBacks (0)

This week’s Nature has an extended climate special made of original research papers, features, commentaries, editorials, essays and book reviews. Here’s the content at a glance.

An uplifting read the package is not, but this will hardly surprise devoted readers of these pages. What’s it all about then? Well, Gavin Schmidt and David Archer, in their news and views piece, get to the heart of it: “Dangerous climate change, even loosely defined, is going to be hard to avoid.”

Some highlights:
Malte Meinshausen and colleagues find that cumulative emissions from 2000 to 2050 of about 1,400 billion tonnes of CO2 yield a 50% probability of exceeding 2 °C warming – the somewhat randomly defined threshold of dangerous climate change - by the end of the twenty-first century Here's an editor's summary of the paper. Just to be clear: Known 2000-2006 emissions were almost 250 billion tonnes.

Myles Allen and colleagues take a slightly different approach to calculating the climate response to anthropogenic emissions. They show that cumulative emissions of one trillion tonnes of carbon (3,670 billion tonnes CO2) over the entire 1750-2050 period yield a 90% probability of warming between 1.3 and 3.9 °C above pre-industrial temperatures, with 2 °C of warming being the best estimate. About half a trillion tonne has been emitted since the onset of industrialization. Here's an editor's summary.

In clear, if we want a reasonably good chance of staying beyond 2°C warming, we cannot afford burning all the oil, gas and coal buried in the ground. We can’t actually afford burning more than half the proven reserves. If we continue burning fossil fuels at current rates we will leave the ‘safety zone’ in less than 20 years. Let’s face it: We have a bad hand – and we can’t bluff the planet.

Continue reading "The wheel of climate fortune" »

Posted by Quirin Schiermeier on April 30, 2009
Categories: Adaptation, Climate Science, Climate prediction, GHG emissions, Quirin Schiermeier, Topics, Uncertainty | Permalink | Comments (0) | TrackBacks (0)

The skies over most land areas are not, as previous studies have suggested, becoming cleaner.
Aerosol pollution has in fact increased most everywhere since 1973, a team reports in Science today (Abstract). Only over Europe have skies brightened, they found.

Kaicun Wang of the University of Maryland, and his colleagues, looked at a 35-year record of clear-sky transparency from 3,250 stations around the world. At many stations visibility had notably decreased - the skies have dimmed.

Air pollution is worst In India, China, Africa and South America, where hundreds of millions are breathing air thick with soot and smog. Clean-air technologies are lacking, or have not yet had much effect, in these regions.

Previous studies concluded that the skies are getting cleaner, and that as a result more sunlight is reaching the surface. Atmospheric scientists believe that aerosols and dust have been shielding us from the worst of global warming.

But the overall cooling effect of aerosols has lately been questioned. The connection between different types of aerosol particles, clouds and solar radiation is more complicated than previously thought. Now it appears as if darker skies don’t necessarily mean less warming, and vice versa. My story
over at Nature News has more about these disturbing uncertainties.

Meanwhile, China is trying hard to reduce air pollution in its most populated cities. Strict regulations aimed at curbing pollution from cars have been set up last year in Beijing and Shanghai.

Quirin Schiermeier

Image: Punchstock

Posted by Quirin Schiermeier on March 13, 2009
Categories: Categories, Atmospheric Science, Quirin Schiermeier, Topics, Uncertainty | Permalink | Comments (0) | TrackBacks (0)

Andrew Revkin of the New York Times has been wondering whether climatologists could help turn down the “rhetorical noise” on recent temperature trends:

Given how much yelling takes place on the Internet, talk radio, and elsewhere over short-term cool and hot spells in relation to global warming, I wanted to find out whether anyone had generated a decent decades-long graph of global temperature trends accounting for, and erasing, the short-term up-and-down flickers from the cyclical shift in the tropical Pacific Ocean known as the El Niño - Southern Oscillation, or ENSO, cycle.

He queried Gavin Schmidt at RealClimate, who’s pondered how to reduce the noise (and beat the rhetoric) on climate trends before. Schmidt thought of the recent Nature paper in which David Thompson et al. removed ENSO fluctuations from the sea surface temperature record (and uncovered an abrupt 1945 temperature drop that they traced to buckets used to collect seawater after World War II).

Continue reading "The global warming signal minus the El Niño noise" »

Posted by Anna Barnett on July 10, 2008
Categories: Anna Barnett, Attribution, Climate Science, Climate variability, Uncertainty | Permalink | Comments (1) | TrackBacks (0)

For all tree huggers out there, this week’s Science is dedicated to ‘forests in flux’, paying tribute to the trees and their contribution to the greater good. A special collection of articles in print, with complementary and online material, examines the fate of the world’s forests, in the face of climate change and an escalating human population.

If it’s been a while since you’ve had the chance to appreciate the languid leafiness of forest foliage, check out the online video. Or for those of you hoping for a more ‘hands on’ experience, there’s a whole section of Science Careers dedicated to opportunities in forest ecology.

There’s lots of serious science, with six Perspectives and one Review by researchers from all over the globe who give their tuppence worth on what’s needed to better understand forests and manage them properly.

Of particular relevance to discussions on how forests can mitigate global warming, Lera Miles and Valerie Kapos have a Perspective highlighting the risks involved in proposed schemes such as REDD (reduced emissions from deforestation and forest degradation) and how to minimize them. Also on this topic, Josep Canadell and Michael Raupach write on what science currently tells us is the best way to manage forests for sequestering carbon.

Drew Purves and Stephen Pacala discuss how forest dynamics remain one of the largest uncertainties in predicting future climate change and detail some of the efforts underway to improve their representation in models. Or for a really solid review of how forests affect climate change, check out Gordan Bonan’s piece here.

Or if that seems like a lot of tree pulp to get through, here are some interesting stats from the issue:

Forests cover ~42 million km2 in tropical, temperate, and boreal lands, and cover ~30% of the land surface

They store ~45% of terrestrial carbon and account for ~50% of terrestrial net primary production.

Forests hold more than double the amount of carbon in the atmosphere.

Carbon uptake by forests in the 1990s contributed to ~33% of anthropogenic carbon emission from fossil fuel and landuse change.

Olive Heffernan

Image: Plantations of Pinus radiata and Eucalyptus nitens in Gippsland (Victoria, Australia); courtesy of Michael Ryan.

Posted by Olive Heffernan on June 13, 2008
Categories: Biodiversity and Ecology, Biosphere feedbacks, Carbon markets, Climate Policy, Climate Science, Climate prediction, Deforestation, GHG emissions, Mitigation, Olive Heffernan, Uncertainty | Permalink | Comments (1) | TrackBacks (0)

Olive Heffernan

In the latest issue of Nature Reports Climate Change, there’s an interesting Commentary by a group of atmospheric scientists who argue that, in assessing the skill of climate models by their ability to reproduce warming over the 20th Century, the latest IPCC Working Group I report may give a false sense of the climate models’ predictive capability.

In ‘Quantifying Climate Change – Too Rosy a Picture?’, Stephen Schwartz of the Brookhaven National Laboratory in Upton, New York; Robert Charlson of the University of Washington, Seattle and Henning Rodhe of Stockholm University, Sweden say that, as it stands, the narrow range of modelled warming misrepresents the certainty with which past temperature changes can be reproduced.

The temperature changes over the 20th Century summarized in the IPCC report represent results from 58 runs with 14 climate models. Although the models fared well at simulating past temperature changes (see Figure 2 for the comparison between simulated and observed warming), Schwarz and co-authors point out the uncertainty range is only half what it would be if uncertainties in the factors driving simulated climate change were accounted for – e.g, cooling by aerosols.

Richard Kerr has an interesting news piece on this Commentary in the July 6 issue of Science entitled ‘Another global warming icon comes under attack’. Kerr’s take on it is that, unlike climate skeptics taking cheap potshots at their choice picks of climate science, the Commentary by Schwarz and co-authors represents a group of mainstream atmospheric scientists challenging an emerging icon of global warming, with climate scientists giving some ground.

Co-author Charlson points out clearly in the Science news piece that “it is not a question of whether the Earth is warming or will continue to warm” under human influence. Rather, Schwarz and co-authors maintain that it is important to give an accurate picture of the range of sensitivities of current models, so that we have a better gauge of what the future might hold.

Kerr reports that IPCC authors say the group has a point, but that their latest WGI report, if read thoroughly, does reflect the uncertainties highlighted in the NRCC Commentary. We will have a response from IPCC authors on the Commentary soon, and will update you when we do....

Posted by Olive Heffernan on July 10, 2007
Categories: Climate Science, In the News, Olive Heffernan, Uncertainty | Permalink | Comments (0) | TrackBacks (0)