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[Due to the increasing size of the archives, each topic page now contains only the prior 365 days of content. Access to older stories is now solely through the Monthly Archive pages or the site search function.]
NASA GISS Study Finds That Methane Has an Elevated Warming Effect Due to Interactions With Aerosols
October 30, 2009
| The 100-year global warming potentials (GWPs) for methane, CO, and NOx (per Tg N) as given in the AR4 and in this study when including no aerosol response; the direct radiative effect of aerosol responses; and the direct+indirect radiative effects of aerosol responses. Source: Shindell at al. Click to enlarge. |
New research by a team at the NASA Goddard Institute for Space Studies (GISS) in New York suggests that gas-aerosol interactions can amplify the global warming impact of some greenhouse gases. In particular, the study led by Drew Shindell found that methane emissions have a larger warming impact due to those interactions than accounted for in current carbon-trading schemes or in the Kyoto Protocol.
Among other conclusions, they found that the 100-year global warming potential (GWP) of methane is ~10% greater (~20 to 40%, including aerosol indirect effects AIE) than earlier estimates that neglected interactions between oxidants and aerosols. Calculations for the shorter 20-year GWP, including aerosol responses, yielded values of 79 and 105 for methane, including direct and direct+indirect radiative effects of aerosols, respectively. The UNIPCC AR4 estimates the 100-year GWP for methane at 25, with a value of 72 for the 20-year GWP.
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Scientists Integrate Nitrogen Cycle into Climate Model; Results Suggests Atmospheric CO2 Concentrations May End Up Higher Than Expected
October 10, 2009
| Schematic illustrating feedback pathways coupling terrestrial carbon and nitrogen cycles in the integrated model. Blue arrows show, in general, the processes represented in previous carbon-only land model components. Orange arrows show the additional processes represented in the coupled carbon-nitrogen land model, differentiated here between rapid internal cycling (solid arrows), and slower fluxes between land pools, the atmosphere, and ground water (dashed arrows). Source: Thornton et al. (2009) |
A team of climate scientists from eight US national labs and academic institutions have successfully incorporated the nitrogen cycle into global simulations for climate change for the first time, questioning previous assumptions regarding carbon feedback and potentially helping to refine model forecasts about global warming.
The results illustrate the complexity of climate modeling by demonstrating how natural processes still have a strong effect on the carbon cycle and climate simulations. In this case, scientists found that the rate of climate change over the next century could be higher than previously anticipated when the requirement of plant nutrients are included in the climate model.
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PBL Study Finds Developed Countries’ Proposals for Copenhagen Fall Short for Reaching 2 °C Climate Objective
October 07, 2009
| The total reductions of the three scenarios used in the PBL analysis. Source: PBL. Click to enlarge. |
The current proposals by developed countries on the table for the upcoming climate negotiations in Copenhagen to reduce greenhouse gas (GHG) emissions do not yet suffice to limit global warming to a rise of 2 °C (based on a long-term 450 ppm concentration of GHG), according to a new report by the Netherlands Environmental Assessment Agency (PBL).
Achieving the 2 °C target—agreed upon by the G8 in July—would require a reduction of 25 to 40% in greenhouse gas emissions in 2020, compared with 1990 levels, whereas the current proposals would lead to a reduction of 10 to 15%. Developed countries as a group would need to increase their reduction targets for 2020 by at least 6 to 10%, in order to keep the 2 °C objective within reach, according to PBL. The global costs would be limited to 0.2% of GDP in 2020.
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Researchers Determine Process Through Which Hydrocarbon Compounds Emitted by Trees Form Aerosols, With Impact on Human Health and Climate
August 09, 2009
| Modeled yield of epoxides from the reaction of isoprene and OH. Grid cells where isoprene mixing ratio is lower than 50 pptv are not shown. Paulot et al. (2009). Click to enlarge. |
A team of researchers from the US, Denmark and New Zealand have discovered a process through which a prevalent biogenic nonmethane hydrocarbon compound emitted by trees—isoprene—forms atmospheric particulate matter (i.e., secondary organic aerosol). The results are published in the 7 August issue of the journal Science.
Aerosols impact human health, due to their ability to penetrate deep into lungs, and impact Earth’s climate through the scattering and absorption of solar radiation and through serving as the nuclei on which clouds form, noted co-author Prof. John Seinfeld from Caltech. “So it is important to know where particles come from.”
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Study Provides Evidence That Low-Level Clouds Act as Positive Feedback to Climate Change
July 26, 2009
| Time series of annual mean values of cloud and climate quantities averaged over the NE Pacific. (A) COADS cloud data. (B) ISCCP cloud data. (C) COADS SST data. (D) Hadley Centre SLP data. Clement et al. (2009), Science. Click to enlarge. |
Low-level stratiform clouds—which play an important climatic role because of their net cooling effect on the global climate—appear to dissipate as the ocean warms, thereby enhancing the warming (i.e., a positive feedback), according to a new study of the NE Pacific by researchers from the University of Miami and UC San Diego. Their paper was published in the 24 July issue of the journal Science.
The study identified decadal fluctuations in cloud cover in multiple, independent cloud data sets. Changes in cloud cover appeared to be linked to changes in both local temperature and large-scale circulation and indicated that clouds act as a positive feedback in this region on decadal time scales. The researchers also found that only one of 18 major global climate models accurately reproduced the observed cloud behavior. That model simulated a reduction in cloud cover over much of the Pacific when greenhouse gases were increased, providing modeling evidence for a positive low-level cloud feedback.
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Researchers Find that CO2 Forcing Alone Doesn’t Explain Magnitude of Ancient Global Warming Episode
July 15, 2009
By analyzing data from deep-sea sediment cores to study an ancient global warming episode (the Paleocene-Eocene Thermal Maximum, PETM), researchers found a less-than two-fold increase (70%) in atmospheric carbon dioxide levels corresponding to the 5–9 °C (9-16 °F) warming of the PETM. Based on current knowledge and models of the Earth’s climate system, they had expected to find a three- to eight-fold increase in atmospheric carbon dioxide levels to drive that amount of warming.
In a paper published online in the journal Nature Geoscience, the team, led by Richard Zeebe of the University of Hawai‘i at Manoa’s School of Ocean and Earth Science and Technology, suggests that in addition to direct CO2 forcing, other processes and/or feedbacks that are hitherto unknown must have caused a substantial portion of the warming during the Paleocene–Eocene Thermal Maximum.
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Researchers Predict Permafrost Thaw Will Intensify Climate Change More Quickly Than Previously Thought; Melting of Greenland Icesheet Could Drive More Water Than Previously Thought to North American Northeast
May 28, 2009
| As areas with permafrost thaw and more old carbon is released, the carbon balance changes. Credit: Zina Deretsky, National Science Foundation. Click to enlarge. |
Permafrost thaw will make potentially significant contributions to atmospheric concentrations of carbon more rapidly that previously thought, according to a new study published in the 28 May issue of the journal Nature.
A separate study led by the National Center for Atmospheric Research (NCAR), which is being published 29 May in Geophysical Research Letters, concluded that the melting of the Greenland ice sheet this century may drive more water than previously thought toward the already threatened coastlines of New York, Boston, Halifax, and other cities in the northeastern United States and Canada.
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Study Concludes That to Limit Global Warming to 2 °C, Less Than 25% of Proven Fossil Fuel Reserves Can be Burnt Between Now and 2050
April 29, 2009
| The theme of the current issue of Nature is that the climate situation may be even worse than you think. |
Less than a quarter of the proven fossil fuel reserves can be burnt and emitted between now and 2050, if global warming is to be limited to two degrees Celsius (2 °C), according to a new study published in the journal Nature today. This issue of Nature—themed “The Coming Climate Crunch”—features a number of related papers and commentary on greenhouse gas emissions and the difficulty of cutting back, as well as an editorial calling on commitment from “the highest levels” to make the needed changes.
The study, led by Malte Meinshausen at the Potsdam Institute for Climate Impact Research (PIK), calculated how much greenhouse gas emissions can be pumped into the atmosphere between now and 2050 to have a reasonable chance of keeping warming lower than 2 °C (above pre-industrial levels)—a goal supported by more than 100 countries to prevent dangerous climate change.
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New Study Shows that Sea Level Rise Resulting From Collapse of West Antarctic Ice Sheet Would be Non-Uniform; Some Regions to See Levels Much Higher Than Previously Predicted
February 06, 2009
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| Sea-level change in response to the collapse of the WAIS computed by using (A) a standard eustatic sea-level theory and (B) the new model. (C) shows the difference between predictions generated by using the two sea-level theories [(B) minus (A)]. Source: Mitrovica et al. (2009) Click to enlarge. |
A new study by researchers at the University of Toronto and Oregon State University concludes that when physical and gravitational factors are applied to projections of sea level rise resulting from a catastrophic collapse of the West Antarctic Ice Sheet, the impact on coastal areas is dramatically worse in some parts of the world than predicted so far.
They found that the catastrophic increase in sea level, already projected to average between 16 and 17 feet around the world (~5m), would be almost 21 feet in such places as Washington, DC, putting it largely underwater. Many coastal areas would be devastated. Much of southern Florida would disappear.
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Study Concludes That Climate Change Alone Could Erode US Improvements in Ground Level Ozone Events Resulting from Reduced Emissions
January 05, 2009
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| Differences in the average (June-August) MDA8-O3 mixing ratios (ppbv) in the surface layer (984-934 hPa) corresponding to (a) climate change under present emissions; (b) A2 emissions change under present climate; (c) climate change under A2 emissions; (d) B1 emissions change under present climate; and (e) climate change under B1 emissions). All differences correspond to 10 year averages. The mean difference is displayed to the left of the panel. Credit: ACS. Click to enlarge. |
Global climate change by itself can significantly worsen the severity and frequency of high ground-level ozone (O3) events over most locations in the US, even with relatively small changes in average O3 air quality, according to a new modeling study by researchers at Carnegie Mellon University.
While changes in US anthropogenic emissions will play the most important role in attaining (or not) near-term US O3 air quality standards, high-O3 increases due to climate change alone can moderately erode an improvement in O3 made under a scenario of reduced US emissions, they concluded. A paper on the study by Pavan Racherla and Peter Adams was published online 30 December 2008 in the ACS journal Environmental Science & Technology.
