Climate and Mosquito-Borne Disease
One of the worlds leading experts on mosquito-borne diseases, Dr. Paul Reiter, with the Center for Disease Control, Dengue Branch, has published a study in the March 2001 supplement of Environmental Health Perspectives. It has been claimed that a warming planet could lead to the spread of mosquito-borne diseases (often erroneously referred to as tropical diseases), such as malaria and yellow and dengue fever into the higher latitudes. Reiter looks at past climate history to better understand how these diseases interact with climate.
To understand how climate affects the transmission rates and geographic ranges of mosquito-borne disease, Reiter examines the historical record of these diseases during the different climatic episodes of the Ice Age, the Medieval Warm Period, which was very similar to the current climate, and the Little Ice Age.
Although Reiter discusses the existence of malaria during the Dark Ages and the Medieval Warm Period, the Little Ice Age is of most interest, since it waned only recently (circa 1850) and was “probably the coldest era of any time since the end of the last major ice age,” according to Reiter. “Yet despite this spectacular cooling, malaria persisted throughout Europe.”
Malaria was found in most of England and parts of Scotland during the 18th and 19th centuries. It was also endemic as far north as Denmark, the coastal areas of southern Norway, and much of southern Sweden and Finland. It was also found in the Baltic provinces of Russia and at similar latitudes in Siberia.
At the end of the Little Ice Age, malaria declined throughout these areas, with the exception of Russia, as global temperatures increased. This was due to several factors that are attributable to greater wealth that resulted from a warmer and more benign climate. Russias volatile political situation throughout the first half of the 20th century prevented the decline of malaria experienced throughout Europe. Reiter gives similar accounts of yellow and dengue fever.
He concludes that although the “recent resurgence of many of these diseases is a major cause for concernit is facile to attribute this resurgence to climate change.”
Indeed, the histories of these three diseases “reveal that climate has rarely been the principal determinant of their prevalence or range; human activities and their impact on local ecology have generally been much more significant. It is therefore inappropriate to use climate-based models to predict future prevalence.”
To Sink or Not to Sink?
According to the New York Times (May 24, 2001), “two new studies are challenging the idea that planting forests could be a cheap way to absorb emissions of carbon dioxide.” The studies appeared in the May 24 issue of Nature.
Unfortunately, the Times and other newspapers have misrepresented what the studies actually say. Rather than looking at whether trees are effective carbon sinks, the studies investigated “the degree to which extra CO2 in the air enables trees to produce extra biomass that removes an additional amount of CO2 from the atmosphere above and beyond the large and visibly-obvious amount trees are currently removing from the air,” according to the CO2 Science Magazine (www.co2science.org). Nearly half of a trees dry mass is made up of carbon extracted from the air.
There are problems with the studies themselves, however. The study by Oren, et al. found that at nutrient-poor sites higher concentrations of CO2 had no detectable effect on the stimulation of biomass growth and only transient effects on nutritionally-moderate sites.
One of the problems with this study, as pointed out by CO2 Science, is that the researchers failed to measure changes in root biomass. Other studies have found similar changes in trunk biomass as the Oren, et al. study, but also found significant increases in root biomass.
The other study by Schlesinger and Lichter looked at carbon storage in soils in forest ecosystems. They found that a 200 parts per million increase in atmospheric CO2 concentrations led to a statistically insignificant rise in the soils total carbon content of 15.5 percent in the top 30 cm of the soil.
At the beginning of the three-year study, the percent carbon values in the soil of the control sites was measured at 1.43 percent and 1.54 at the CO2-enriched sites. At the end of the experiment, the control sites percent carbon value dropped to 1.31 percent while the CO2-enriched sites increased to 1.59 percent.
“Viewed in this light,” according to CO2 Science, “the importance of atmospheric CO2 enrichment to soil carbon sequestration is immediately obvious. Under the site-specific conditions of the study in question, the soils of the forest plots growing in ambient air were actually losing carbon, i.e., they were carbon sources; while the soils of the plots exposed to the extra 200 ppm of CO2 were gaining carbon, i.e., they were carbon sinks.”
Of Sun and Things
Three new studies looking at how changes in solar radiation affect the climate have recently appeared, further confirming the suggested link between solar and climate dynamics.
A study in Science (May 18, 2001) used lake-sediment cores from the Yucatan Peninsula, Mexico to reconstruct the regions climate history for the last 2,600 years. The reconstruction revealed a drought cycle of 208 years, which is similar to a 206-year variation in solar activity. The researchers conclude, “that a significant component of century-scale variability in the Yucatan droughts is explained by solar forcing,” which also “correspond with discontinuities in Maya cultural evolution.”
A Nature study (May 17, 2001) used stalagmite samples from northern Oman in Arabia as a proxy for variations in the tropical circulation and monsoon rainfall in the Indian Ocean over a period of 9.6 to 6.1 thousand years to the present. They compared this record to a record of changes in solar activity. “The excellent correlation between the two records suggests that one of the primary controls on centennial- to decadal-scale changes in tropical rainfall and monsoon intensity during this time are variations in solar radiation,” conclude the researchers.
Finally, Geophysical Research Letters (28: 2001) has published a study looking at how changes in the cosmic ray flux, caused by solar variation, affect precipitation. Using data on the cosmic ray flux recorded by ground-based neutron monitors and precipitation data from the National Oceanic and Atmospheric Administrations Climate Prediction Center Merged Analysis of Precipitation, the researchers found “evidence of a statistically strong relationship between cosmic ray flux, precipitation and precipitation efficiency over ocean surfaces at mid to high latitudes.”
Etc.
- In a May 3 speech to the Science and Technology Policy Colloquium sponsored by the American Association for the Advancement of Science, Larry Lindsey, Assistant to the President for Economic Policy said the following about the Kyoto Protocol:
“This financial math is important when considering some of the biggest environmental challenges one faces today. When confronting long-run challenges – and the environment is certainly one of these – investments in the research and development of new technologies, with actual applications decades in the future, are far more cost-effective than trying to act with existing technologies.
“It is for precisely this reason that the Administration opposes the Kyoto protocol. We believe the Kyoto protocol could damage our collective prosperity and, in so doing, actually put our long-term environmental health at risk. Fundamentally, we believe that the protocol both will fail to significantly reduce the long- term risks posed by climate change and, in the short run, will seriously impede our ability to meet our energy needs and economic growth. Further, by imposing high regulatory and economic costs, it may actually reduce our capacity both to find innovative ways out of the environmental consequences of global warming and to achieve the necessary increases in energy production.” The full speech is available at www.aaas.org/spp/dspp/rd/colloqu.htm.
- The Atmospheric Division of Australias Commonwealth Science and Industry Research Organization (CSIRO) has released a new global warming brochure, Climate Change: Projections for Australia, filled with the usual scare stories about floods, droughts, heat waves, etc. The following appears at the end of the report (see www.john-daly.com):
Disclaimer
The projections are based on results from computer models that involve simplifications of real physical processes that are not fully understood. Accordingly, no responsibility will be accepted by CSIRO for the accuracy of the projections inferred from this brochure or for any persons interpretations, deductions, conclusions or actions in reliance on this information.