Orange County Global Warming Committee

Atmosphere

Introduction

Interactions With Aerosols Boost Warming Potential of Some Gases – 31 Oct 2009
Global Increase in Methane Due to Unusual Arctic Warmth, Tropical Wetness – 28 Sep 2009
Clouds Appear to Be Big, Bad Player in Global Warming – 24 Jul 2009
Aerosols May Drive a Significant Portion of Arctic Warming – 9 Apr 2009

Weather

Global Surface Temperature was Second Warmest for September – 16 Oct 2009
Heavier Rainstorms Ahead Due to Global Climate Change– 27 Sep 2009
Global Warming May Dent El Niño's Protective Shield From Atlantic Hurricanes, Increase Droughts – 24 Sep 2009
Recent Warming Reverses Long-Term Arctic Cooling – 4 Sep 2009
Global Ocean Surface Temperature Warmest on Record For June – 27 Jul 2009
Medieval Storms Portend Worse Hurricanes – 12 Aug 2009

Atmosphere articles

Introduction
Greenhouse gases are components of the atmosphere absorb and emit solar radiation. The main greenhouse gases are water vapor, carbon dioxide, methane, nitrous oxide, and ozone.
Aerosols are solid particles or liquid droplets suspended in air. They include soot, dust, and sulfur dioxide particles and are created from industrial processes and burning fossil fuel and biofuels, including forest fires. They are also a health hazard. Aerosol particles may either reflect sunlight back into space, resulting in cooling, or absorb sunlight, causing warming. Aerosols also influence the formation and properties of clouds.
By contrast, greenhouse gases such as carbon dioxide and methane have no effect on visibility. Solar radiation passes right through them. They cause global warming by trapping the solar energy that is absorbed at the earth's surface and prevent it from being radiated as heat back into space.

Article from Science News 31 October 2009

Interactions With Aerosols Boost Warming Potential of Some Gases

Climate models are based on the best knowledge available. As new information become available, the models change. Recent evidence that may influence climate modeling is that some the global warming potential of some greenhouse gases are closely linked with aerosols and that amplifying interactions occur between individual components of the atmosphere. Methane and carbon monoxide, for example, may have a have a substantially more powerful warming effect than was previously thought.
Methane, carbon monoxide, and other gases are components of a complicated cascade of chemical reactions that also compete with aerosols for the highly reactive molecules that cleanse the air of pollutants.
Sulfate aerosols are produced indirectly from coal burning and other industrial processes that release sulfur dioxide. The sulfur dioxide reacts with hydroxyl radicals in the air to produce sulfates. Hydroxyls are considered atmospheric "scrubbers" because they remove many types of pollution from the atmosphere. Nitrate aerosols also react with hydroxyls. When methane and carbon monoxide are present, they compete with nitrates and sulfates for reactive hydroxyls. With less conversion of sulfur dioxide to sulfate, there is more warming.
Modeling has estimated that increases in global methane emissions have caused a 26 percent decrease in hydroxyls and an 11 percent decrease in sulfate aerosols. Reducing sulfate unmasks methane's warming by 20 to 40 percent over current estimates, but also helps reduce negative health effects from sulfate aerosols. Models also estimated that global carbon monoxide emissions have caused a 13 percent reduction in hydroxyls and 9 percent reduction in sulfate aerosols.
Up to now the effect of greenhouse gases was based on their individual concentrations in the atmosphere. This approach serves as the foundation of climate treaties such as the Kyoto Protocol or cap-and-trade plans, but it doesn’t account for interactions that occur between individual atmospheric components
It may be more important to look at all of the greenhouse gases, not just carbon dioxide. The latest evidence suggests that all the non-carbon dioxide greenhouse gases combined have an equal or greater impact on climate. Reducing methane emissions may be easier to accomplish than reducing carbon dioxide.
Link: http://www.sciencedaily.com/releases/2009/10/091030100020.htm

Article in Science Daily 28 September 2009

Global Increase in Methane Caused by Unusual Arctic Warmth, Tropical Wetness

Methane is a much more active greenhouse gas than carbon dioxide. However, for many years atmospheric concentrations remained about the same from year to year. That situation changed in 2007, when methane levels began to increase.
NOAA’s Earth System Research Laboratory (Boulder, Colorado) compiled data on weekly methane measurements taken at 46 locations around the world between 1983 and 2008 and compared the results with known weather phenomena. The results are published in the September issue of Geophysical Research Letters.
According to NOAA scientist Ed Dlugokencky, 3 factors may have been involved in the increased methane concentrations – excessive warmth in the Arctic, tropical forest burning, and more rain in Indonesia and the Amazon.
Increased rainfall in the tropics may have promoted the growth of methane-producing microbes. La Nina conditions were prevalent in the middle of 2007, waned, and then intensified in 2008. La Nina brought excessive rainfall and cooler sea surface temperature in the eastern and central tropical Pacific Ocean and wetter fall and winter seasons in the Pacific Northwest. La Niña also tends to bring drier conditions in the Central and Southwest Plains regions.
Biomass burning observed from ground sites and satellites probably contributed about 20% of the methane released in 2007. However, there was a substantial increase in methane release measured in northern wetland regions. That year was the warmest on record for the Arctic, which may have promoted a process that converts carbon trapped in permafrost to methane and the release of methane hydrates.
Methane is typically created in low-oxygen conditions, such as the digestive tracts of ruminant animals, peat bogs, rice paddies, flooded wetlands, landfills, and termite colonies. The gas is also emitted in forest fires and it can escape during fossil fuel extraction and distribution.
Link: http://www.sciencedaily.com/releases/2009/09/090927151132.htm

Summary article from Science 24 July 2009 by Richard Kerr

Clouds Appear to Be Big, Bad Player in Global Warming

As carbon dioxide levels in the atmosphere increase along with surface temperatures, one of the unknown influences on global warming is cloud formation. If clouds thicken they could effectively shade the planet and help reduce global warming; but if they thin and disappear they could be amplifying the problem.
The results of an analysis of cloud behavior over the recent warming period suggest that clouds may be strongly amplifying the warming. If true, climate models will have to be reworked to include these effects. Climate modeler Gerald Meehl (National Center for Atmospheric Research in Boulder, Colorado) thinks that global warming could be worse than most models predict.
The effect of clouds has been a mystery because there is little data. Amy Clement’s team at the University of Miami in Florida have evaluated 2 historic long-term “eyeball” records of cloud behavior collected by mariners from an area that covers the ocean over the subtropics from Hawaii to Mexico between 1952 to 2006. Satellite records over 1984 to 2005 were also used.
The data covered the two major climate shifts in the North Pacific that occurred during the observation period. During a warming episode that began in 1976, there was a decrease in the extent of cloud cover reported from the ships as ocean temperatures increased. This suggested that ocean warming transferred heat to the atmosphere and caused low-lying clouds to thin, creating a positive feedback to solar warming. During a cooling period that occurred during the late 1990s, there was an opposite thickening effect on clouds.
The hypothesis that there is a positive low-cloud feedback to global warming was supported by satellite data that showed additional solar warming with decreased cloud cover, and he added atmospheric warmth was sufficient to account for the degree of ocean warming.
To evaluate whether positive feedback could be observed in climate models, Clement’s group examined several models. Only 2 models predicted that low clouds were responsible for a positive feedback in warming. The HadGEM1 model from the United Kingdom (Hadley Center in Exeter) produced the most realistic results, especially in the 2 lowest kilometers of atmosphere, where the low-lying clouds are found. HadGEM1 is also the most sensitive of the 18 models to added greenhouse gases. When carbon dioxide concentrations doubled, the model predicted a 4.4°C temperature rise, whereas the median rise for all 18 models is 3.1°C. This difference raises a red flag.
Although the study suggests that low-lying clouds amplify global warming, the results are not proof. An important contribution of this study is that it should lead to improvements in climate models.
Research article: Clement, Brugman, and Norris et al (2009). Observational and model evidence for positive low-level cloud feedback, Science, 325 (5939) 460.

Article from SciencDaily 9 April 2009

Aerosols May Drive a Significant Portion of Arctic Warming

New data from NASA suggests that changes in tiny airborne particles called aerosols may be responsible for much of the atmospheric warming observed in the Arctic in the past 30 years. Aerosols can directly influence climate by reflecting or absorbing the sun's radiation, and they can change the properties of clouds.
Drew Shindell and his team at NASA Goddard Institute for Space Studies in New York, used modeling to determine the sensitivity of different regional climates to changes in carbon dioxide, ozone, and aerosol concentrations. Mid and high latitudes were particularly sensitive. The model suggested that aerosols may account for nearly half of the warming in the Arctic during the last 3 decades. Sulfates and black carbon seem to play a critical role in regulating climate change.
Sulfates, which are derived primarily from the burning of coal and oil, scatter solar radiation and thus have a cooling effect. Over the past 30 years, because of laws passed in the US and Europe, sulfate emissions have decreased by 50 percent, which would result in a cooling effect.
Over the same period, black carbon emissions have risen, largely from Asia. Black carbon is small, soot-like particles produced primarily by burning biofuels. These particles absorb incoming solar radiation, thus warming the planet.
The researchers evaluated the relative roles of different components of the climate system, including solar variations, volcanic events, and greenhouse gas levels in the presence of different levels of aerosols. When they determined how much warming could be attributed to each variable, aerosols loomed large.
This finding has implications for policymakers. It refocuses attention on atmospheric components other than carbon dioxide. It will be important to better understanding how aerosols behave in the atmosphere. To this end, NASA's Glory satellite with enhanced aerosol measurement capabilities will be launched soon.
Journal reference:
Shindell D, Faluvegi G. Climate response to regional radiative forcing during the twentieth century. Nature Geoscience, 2009; 2 (4): 294 DOI: 10.1038/ngeo473
Link: http://www.sciencedaily.com/releases/2009/04/090408164413.htm

Weather articles

Article from Science Daily 16 October 2009

Global Surface Temperature was Second Warmest for September

According to NOAA’s National Climatic Data Center (NCDC), September 2009 was the second warmest for global surface temperature since records began in 1880. The record was set in 2005. From an average combined global land and ocean surface temperature of 59.0 degrees F since 1880, September was 1.12 degrees F higher. September was 1.75 degrees F hotter than the 20th century average temperature for September of 53.6 degrees F.
Warmer-than-average temperatures were experienced by most land areas. The greatest warmth occurred across Canada, and the northern and western contiguous United States were substantially warmer than average, as was Europe, most of Asia, and Australia.
The global ocean temperature for September tied with 2004 as the fifth warmest on record, 0.90 degree F above the 20th century average of 61.1 degrees F. By contrast, the Gulf of Alaska and the near-Antarctic southern ocean were cooler than average.
In related events, the Arctic sea ice area was the 3rd lowest for any September since records began in 1979. Sea ice area in the Arctic was 23.8 percent lower than the 1979-2000 average. By contrast, sea ice area in the Antarctic was 2.2 percent greater than the 1979-2000 average.
Link: http://www.sciencedaily.com/releases/2009/10/091016140633.htm#

Article in Science Daily 27 September 2009

Heavier Rainstorms Ahead Due To Global Climate Change

According to researchers at MIT and Caltech, it is now clear that global climate change will affect weather patterns by causing heavier rainstorms outside of the tropics. Estimates based on climate modeling indicate that higher average annual precipitation will occur in deep tropics and temperate zones, but the results for the subtropics are inconsistent. Heavy downpours are serious because they can cause increased flooding and soil erosion.
Paul O'Gorman (Department of Earth, Atmospheric and Planetary Sciences at MIT) and Tapio Schneider, (Environmental Science and Engineering at Caltech) have reported that their model simulations indicate that for every one degree Celsius of warming will result in an increase in the frequency of heavy precipitation by 6 percent. Based on warming projections 5 degrees Celsius by 2100, thus a 30% increase in frequency of heavy storms could be expected.
The climate models are less consistent about what will happen to precipitation extremes in the tropics because typical weather systems in those regions fall below the size limitations of the models.
Link: http://www.sciencedaily.com/releases/2009/08/090817190638.htm

Article from Science Daily 24 Sep 2009

Global Warming May Dent El Niño's Protective Shield From Atlantic Hurricanes, Increase Droughts

El Niño weather patterns protect the Caribbean and Eastern US from hurricanes in the Atlantic. According to Ben Kirtman (Rosentstiel School of Marine and Atmospheric Science, University of Miami) and his team, there are 2 types of El Niños, one in the eastern Pacific and one in the central Pacific, and the central type of pattern is increasing.
El Niño is a warm water current along that recurs along the equator in the Pacific Ocean and affects weather in the tropics. When it increases wind sheer in the Atlantic, it dampens the occurrence of major hurricanes in that region. The central El Nino affects currents near the International Dateline, and seems to cause more severe droughts in Australia and India as well decreasing the beneficial effects of its eastern brother.
Sang-Wook Yeh (Korea Ocean Research & Development Institute) and his team applied sea surface temperature data from the Pacific Ocean over the past 150 years to 11 climate change models from the Intergovernmental Panel on Climate Change. In 8 of the models, warming conditions increased the incidence of the central Pacific type of El Niño. Actual occurrences of central El Niño over the past 20 years have increased in frequency from 1 out of 5 to 1 out of 2 weather patterns. The effects of these events are likely to be substantial as the climate warms.
The centers of the central and eastern El Niños are approximately 4,100 miles apart, and yet they appear to influence each other. The central El Niño shields the Caribbean and eastern US from hurricanes. An eastern Pacfic El Nino is developing this year, and it is probably responsible for the mild hurricane season in the Atlantic. Meterologists anticipate that the southern US will be wet and the northeast dry and warm this winter. They also expect this El Niño event to end by next spring and to be followed by a La Niña event, which may generate more intense Atlantic hurricanes in 2010.
Link: http://www.sciencedaily.com/releases/2009/09/090923143337.htm

Article from Science 4 September 2009

Recent Warming Reverses Long-Term Arctic Cooling

To investigate the temperature history of the Arctic during the first millennium, a team of scientists with the Arctic Lakes 2k Project constructed a proxy temperature record for the past 2000 years from lake, ice core, and tree ring data. This record showed a cooling trend that occurred between 2000 years ago and the 20th century that reversed during the 20th century, producing 4 out of 5 of our warmest decades between 1950 and 2000.
The Arctic Lakes 2k study produced a decade-by-decade compilation of Arctic (poleward of 60°N) lake data combined with ice core and tree ring data to form a proxy record of Arctic climate for the past 2000 years. Lakes occur throughout the Arctic, and they are the source of the most accessible and consistent proxy data for the late Holocene (13,000 years ago to the present). These records include data from the Little Ice Age temperature anomaly (1400 to 1800), during which the coldest temperatures within the past 8000 years occurred in the Arctic, and the Medival Warm Period (1100 to 1300).
The evidence shows a cooling trend from 1 CE to 1900 CE. This trend is especially clear in records from ice and lakes. The data showed a cooling trend of –0.22-degrees C per 1000 years. This trend is consistent with a similar to one that occurred between 10,000 and 6000 years ago. Peak temperatures during the Holocene thermal maximum were 1.6‑degrees C higher than the average temperature of the 20th century, and the subsequent rate of cooling was –0.11 to ‑0.32-degrees C per 1000 years.
These cooling trends correlate primarily with a reduced summer solar radiation exposure due to precession of the Earth’s orbit, tilting the planet so that the Arctic is further away from the Sun during the summer. This is enhanced by a positive feedback effect of snowpack and sea-ice, which are capable of reflecting solar radiation and reversing its warming effects (albedo effect). The area of snowpack and ice is sensitive to changes in solar radiation. As snowpack and sea ice area expands during a cooling trend the amount of heat reflected by the ice increases.
The intense warming that occurred in the 20th century contrasts sharply with the earlier cooling trend. If the cooling trend in the Arctic had continued, the current expected average summer temperature would be –0.5°C between 1961 and 1990. Instead, there was a increase in temperature. This warming trend coincided with increased emissions of greenhouse gases by human activities, with no contribution by major volcanic eruptions or changes in solar activity.
Arctic warming in the 20th century was more severe than in any other part of the Earth, probably due to a combination of natural variability and the heat reflecting effects of snow and ice cover. Four out of 5 of the warmest decades in the Arctic were between 1950 and 2000.
The 1000-year cooling of –0.22-degrees C per 1000 years was the strongest trend in the proxy temperature record. This cooling corresponded with the slow decrease in solar radiation exposure at high northern latitudes with changes in the tilt of the Earth relative to the Sun. The continuing decrease in solar radiation exposure should lead to a cooling trend in the Arctic. Instead, there is a warming trend, and the most recent decade was warmer than any in the previous 200 decades.
Journal reference: Kaufman and the Arctic Lakes 2k Project Members, Science Sep 2009, Vol 325, No 5945 pp 1236-1239.
Link: http://www.sciencemag.org/cgi/content/full/325/5945/1236

Article from ScienceNOW Daily News 12 Aug 2009 by Phil Berardelli

Medieval Storms Portend Worse Hurricanes

Evidence from ocean sediments indicate that our current climate is similar to a period of increased hurricane activity that occurred about 1000 years ago.
For over 10 years, scientists have sought to determine whether climate change is causing intense storms and hurricanes. A team of researchers directed by Michael Mann (Meteorologist, Pennsylvania State University) has investigated drill cores from 8 sites in coastal waters of Eastern US and Puerto Rico to look for evidence for storm-related sediment disturbance. This approach provided a reliable 1500-year record of significant storms, and was combined with other information providing data on water temperatures and storm intensity. The results have been published in Nature.
The coastal sediment evidence shows that the maximum average of 15 Atlantic hurricanes per year was reached about 1000 years ago. This level was unmatched up until the last 15 years. Water temperatures 1000 years ago were warm, but not as warm as today. At the same time, waters of the Pacific Ocean were relatively cool due to La Niña weather patterns. Warm water in the Atlantic causes more storms, while warm water in the Pacific creates stronger jet streams that tend to disrupt storms in the Atlantic. The dual weather conditions produce stronger and more frequent hurricanes.
Examination of coastal sediments revealed a connection between warmer water and hurricane frequency during the past 150 years. With cooler ocean temperatures there were 7-8 hurricanes a year, while the warmer waters that occurred in recent years produced 15 hurricanes on average each year. Mann thinks that we will likely see stronger and more frequent hurricanes in the near future.
Link: http://sciencenow.sciencemag.org/cgi/content/full/2009/812/1

Article from Science Daily 27 July 2009

Global Ocean Surface Temperature Warmest on Record For June

In June of 2009, global ocean surface temperature was the warmest on record for June since records began in 1880. June’s temperature broke the previous record set in 2005. The combined land and ocean surface temperature for June was 1.12 degrees F greater than the 20th century June average of 59.9 degrees F. For ocean surface temperature alone, June was 1.06 degrees F above the 20th century June average of 61.5 degrees F. Both hemispheres broke their June records for warmest ocean surface temperature. The land surface temperature for June 2009 was 6th warmest on record.
Land surface warmth was especially high in Africa, Siberia and around the Mediterranean and Black Seas. Cooler-than-average average June temperatures were noted in central Asia, the Northern Plains of the US, and Canadian Prairie Provinces.
Link: http://www.sciencedaily.com/releases/2009/07/090725120303.htm