Still No Consensus on Global Warming Science

Published January 1, 2003

Several new studies show human-induced global warming is probably not occurring. Additionally, new studies of rainfall patterns, Mediterranean plant life, and African desert climate show recent increases in atmospheric CO2 benefit the planet’s vegetation and animal life.

Falling Temperatures in Store

As much as one-half of all global surface warming since the 1970s may simply reflect natural climate variation, concludes a new Texas A&M study. Researchers analyzed long-term changes in Pacific Ocean temperatures to conclude natural climate variations occur in cycles of up to 25 years.

“The phenomenon looks like El Niño, but with a much longer time scale–El Niño occurs over a period of from nine to 12 months, but this fluctuation lasts for about 25 years,” said Benjamin Giese, oceanography professor at the Texas A&M College of Geosciences.

Giese noted that in 1976 an abrupt change in the temperature of the tropical Pacific Ocean preceded a rise of two-tenths of a degree in global air temperatures. He reports that conditions are now similar to the conditions that existed prior to the 1976 climate shift, except with the opposite sign. If conditions develop in a similar way, then the tropical Pacific could cool back to pre-1976 conditions.

“The subsurface tropical Pacific has shown a distinct cooling trend over the last eight years,” Giese reported.

According to the climate histories, long-term changes in Pacific Ocean temperatures precede global surface air temperature changes. “The possibility exists that the warming trend in global surface air temperatures observed since the 1970s may soon weaken,” writes Giese.

“This natural variation would help to counter the greenhouse gas warming effect. In fact, careful study reveals that global warming and cooling has occurred in the past in cyclical patterns.”

Most Reliable Data Show No Warming Trend

Debate continues on whether human-collected data at surface weather stations, such as airports, is less reliable than satellite records. Surface weather station readings show an increase of about 0.12° Celsius per decade, but urban growth frequently creates artificial heat islands that interfere with these stations.

The lower atmosphere, where scientists predict the first and most dramatic signs of global warming should appear, is unaffected by urban heat island effects and is monitored continuously by NASA satellites, thought to be accurate to within 0.01° C. There has been no overall warming of the lower atmosphere since the satellites began taking measurements in 1979.

In the Journal of Climate (Vol. 15: 2412-2428 (2002)), G.C. Hegerl and J.M. Wallace set out to reconcile the growing gap between land-based and satellite temperature readings. After extensive analysis, the authors found “no mechanism with clear spatial or time structure explains trends in the observed lapse rate.” Moreover, “all attempts to explain all or a significant part of the observed lapse rate trend by modes of climate variability with structured patterns from observations have failed.”

According to the Center for the Study of Carbon Dioxide and Global Change, “the reasons why no explanation can be found for the ever-increasing difference between the surface and satellite temperature trends of the past 20-plus years may be that one of the temperature readings is incorrect.” The evidence, it says, points to human error in the land-based temperature record.

“It would be extremely easy for a spurious warming of 0.12° Celsius per decade to be introduced into the surface air temperature trend as a consequence of the order-of-magnitude greater anthropogenic-induced (heat-island-type) warming that occurs in most of the places where land-surface air temperature measurements are made, due to increases in human population and urban development.”

Until the human-collected surface readings can be reconciled with the precise lower atmosphere readings taken by satellite, it would be scientifically reckless to conclude global warming is occurring, concludes the Center.

Sea-Ice Season in Antarctic Growing Longer

A study reported in Annals of Glaciology (Vol. 34: 435-440 (2002)) found sea ice in the Southern Ocean region surrounding Antarctica has exhibited mixed trends of growth and shrinkage, depending on the area studied. However, according to the study’s author, “the area of the Southern Ocean experiencing a lengthening of the sea-ice season by at least 1 day per year over the period 1979-99 is 5.6 x 10(6) km2, whereas the area experiencing a shortening of the sea-ice season by at least 1 day per year is 46 percent less than that, at 3.0 x 10(6) km2.”

Accordingly, “a much larger area of the Southern Ocean experienced an overall lengthening of the sea-ice season over the 21 years 1979-99 than experienced a shortening.” The lengthening sea-ice season is the opposite of what climate models predict would happen in a warming world.

Arctic Ice Thickness Shows No Change

A recent study in Geophysical Research Letters (Vol. 28: 1039-1041 (2001)), found there has been no significant change, one way or another, in Arctic sea ice thickness. “[M]ean ice thickness has remained on a near-constant level around the North Pole from 1986-1997,” notes the study’s author. The data was obtained from six submarine cruises that traversed the central Arctic Basin taking measurements.

The unchanged sea ice thickness is particularly damaging to claims of global warming because warming alarmists have lately claimed that either decreasing or increasing Arctic ice cover are signs of global warming. This intellectual dexterity turns the global warming thesis into an untestable hypothesis, which is convenient for a certain kind of “the facts don’t matter” radical environmentalism, but is not sound science. Evidence of long-term consistency in Arctic sea-ice thickness defies global warming predictions even in the context of the untestable hypothesis.

Rising CO2, Shrinking Deserts

Several new studies indicate increasing levels of atmospheric CO2 benefit global plant life. A study on variations in northern vegetation inferred from satellite data from 1981-1999, reported in Journal of Geophysical Research (Vol. 106: 20,069-20,083 (2001)), found an 8 to 12 percent increase in vegetation across North America and Eurasia, respectively. A subsequent comment in the same journal, Journal of Geophysical Research (Vol. 107, 10.1029/2001389), employed statistical analysis to conclude that a concurrent rise in atmospheric CO2 was primarily responsible for the increased vegetation.

An article in the September 16, 2002 issue of New Scientist magazine reports “Africa’s deserts are in ‘spectacular’ retreat.” The article documents how vegetation is reclaiming large expanses of barren land across the entire southern edge of the Sahara desert. This evidence directly contradicts statements by climate change alarmists that global warming is already having an adverse affect on poor and underdeveloped African nations by increasing desertification.

According to the author of the study, Frank Pearce, “the southern Sahara desert is in retreat, making farming viable again in what were some of the most arid parts of Africa. … Burkina Faso, one of the West African countries devastated by drought and advancing deserts 20 years ago, is growing so much greener that families who fled to wetter coastal regions are starting to go home.”

An additional study, reported in Functional Plant Biology (Vol. 29: 1097-1106 (2002)), discovered Mediterranean shrubs were exhibiting seasonal improvements in tissue elasticity and water transport efficiency under natural long-term CO2 enrichment. The plants’ ability to produce greater tissue elasticity under CO2-enriched conditions provided evidence that these and other plants will increase their drought tolerance with growing levels of atmospheric CO2.

Finally, evidence continues to mount that recent increases in atmospheric CO2 are resulting in a moderate increase in beneficial rainfall in the U.S. Climatologist Patrick Michaels reports in an accompanying Environment & Climate News story that U.S. precipitation has increased about 10 percent over the 20th century, an increase of roughly 3 inches in the last 100 years. “If anything, global warming is making us wetter,” Michaels reports.

James M. Taylor is managing editor of Environment & Climate News.