The 2007 report of the Intergovernmental Panel on Climate Change concluded that “more intense and longer droughts have been observed over wider areas since the 1970s.” Its findings were largely based on a widely used model known as the Palmer Drought Severity Index, which uses temperature and rainfall to determine dryness. Originally developed in the 1960s to help apportion aid to drought-stricken farmers, the index may skew drought trends in the presence of climate change.
“It’s quite obvious that the Palmer model has been overestimating changes in drought." Other scientists have reported this effect for regional areas, but the new study is the first to show it globally. The problem has to do with the way of calculating a quantity called potential evaporation, the amount of evaporation that would occur given an unlimited water supply. Historically, scientists calculated potential evaporation using the Thornthwaite equation, which is based entirely on temperature. The more complete Penman-Monteith equation, by contrast, incorporates the influences of solar radiation, humidity and wind speed. The latter gives a much more accurate measure of potential evaporation.
Scientists calculated global drought trends from 1950 to 2008 using both equations on multiple datasets. Notably, they found a much smaller change in drought using the Penman-Monteith equation. The estimated yearly drought increase was only half as severe as that derived from the Thornthwaite equation. The weather records invariably contain some errors, but those errors don’t alter the conclusion that the simpler model overestimates rises in global drying.
The finding comes in stark opposition to the results of several recent studies. An atmospheric scientist's own research suggests that the two equations yield very little difference in drought estimates. He says the new study fails to consider trends in soil moisture and other variables. He also claims that the new study relies on outdated weather records and questionable radiation data.
If drought increases have in fact been overestimated, scientists may need to rethink how global warming may affect extreme weather going forward. One thing scientists seem to agree on is that the Palmer metric for drought will become increasingly inaccurate in future. “I think we’re converging on the realization that it’s not just about temperature."
**Positive anything is better than negative thinking.**
Elbert Hubbard
LARGEST QUAKES -
Live Seismograms - Worldwide (update every 30 minutes)
This morning -
5.4 NEAR EAST COAST OF HONSHU, JAPAN
5.2 PACIFIC-ANTARCTIC RIDGE
5.0 ANTOFAGASTA, CHILE
Yesterday -
11/15/12 -
5.0 OFF W COAST OF NORTHERN SUMATRA
5.7 NEAR ISLANDS, ALEUTIAN ISLANDS
6.0 ESTADO DE MEXICO, MEXICO
5.9 BISMARCK SEA
5.0 OFFSHORE GUATEMALA
11/14/12 -
5.5 NEW BRITAIN REGION, P.N.G.
6.1 ATACAMA, CHILE
5.3 FIJI REGION
5.0 TONGA
5.6 PANAY, PHILIPPINES
Cluster of moderate quakes in the DODECANESE ISLANDS, GREECE continued.
6.0 quake shakes west and central Mexico - no reports of significant damage. The 3:20 a.m.quake struck near the town of Tlalchapa in the state of Guerrero and about 107 miles (173 kilometers) southwest of Mexico City. It set off alarms in Mexico's capital on Thursday, but there were no reports of injuries or significant damage.
VOLCANOES -
Volcano Webcams
New Zealand - Mt Ruapehu may be entering another stage of eruption as temperatures underneath the crater lake rise and pressure may be building up from a blocked vent.
Popocatepetl volcano (Mexico) is clearly ramping-up in its activity since the weekend. CENAPRED reports nearly 200 exhalations of gas and ash and the Popo seismogram is showing increased local seismicity as well.
Three Indonesian Volcanoes Rumbling - Raung, Sangeang Api and Rokatenda.
TROPICAL STORMS -
No tropical storms.
Thailand - Tropical storm prompts alerts for South, Gulf. The government has gone on alert for a tropical depression in the South China Sea, expected to enter the Gulf of Thailand this weekend. The storm, located about 400 kilometres southeast of Ho Chi Minh City in Vietnam, is moving west slowly.
Weather service confirms Sandy churned up RECORD-HIGH WAVES off the New Jersey and New York coasts - “It is safe to say that both National Data Buoy locations nearest Sandy Hook achieved a recent record extreme sea state on top of and probably very close to the time of the record storm tide at Sandy Hook."
EXTREME HEAT & DROUGHT / CLIMATE CHANGE -
The U.S. Midwest drought was the worst since 1956, cutting corn output by 13 percent and forcing cattle ranchers to shrink the U.S. herd to a 39-YEAR LOW.
Worsening Tanzania drought drives youth to the cities - Changing weather patterns in Tanzania have caused a rising wave of migration from rural to urban areas, with thousands of youths flocking into Dar es Salaam, the largest city, in search of work.
