http://english.peopledaily.com.cn/90001/90777/90856/7088694.html

Climate experts still can't be sure whether global warming has caused the excruciating heat waves which are currently grilling nations in the northern hemisphere such as China, Japan, the United States and Russia, and constantly refresh their power demand records.

Scientists believe the present hot weather is formed by a pack of reasons instead of a single one, meaning the global warming.
Dr. Alexander Frolov, chief of the Russian Federal Service for Hydrometeorology (Roshydromet), said the high temperature cannot either prove or deny the global warming theory, because meteorology is a statistical science, which requires substantial and coherent data.
He said the only credible signal of a warming planet is for such hot weather to repeat annually, or at least every five years, for three decades. He also admitted 2010 would be the hottest year ever since humans began to ink such records.
The U.S. National Center for Atmospheric Research (NCAR) said in its report in early 2009 that the hottest days were over twice as many as the coldest days in America over the past 10 years, adding that the number of the hottest days would continue to surge in the future.
Thus, the canicule, which is cooking the eastern part of the United States, has been taken as a proof of the report's projections.
The United Nations also said in its report that global warming would reliably create extreme weather like heat waves and storms.
As these experts cannot confirm the culprit of the miserable weather, their explanations, apart from global warming, vary from one to another, including abnormal atmospheric circulation and El Nino.
They agree that, according to the scientific theory, high temperature is a direct result of warm high or warm anticyclone, which, if it maintains hovering over a certain place, would trigger long term heat waves.
Yoshihiro Tchibana, an Earth environmental meteorology professor at Japan's Mie University, said broiling summers due to anticyclone seem to arrive roughly every 10 years.
Japan's Meteorological Agency further elaborated on the anticyclone theory. The agency said the westerly wind, which usually rounds the Earth along a oblique route. However, it made an unexpected turn towards the North Pole in early July, leaving much of the middle-latitude zone in the boiling heat.
Shotaro Tanaka, scientific officer at the agency, said besides these hot middle-latitude areas, oceans and underpopulated regions are rather cool, adding that not the entire globe is warming up.
Jay Lawrimore, chief of climate analysis at the federal National Climatic Data Center (NCDC), said El Nino is also behind the scene.
The phenomenon refers to warm ocean current that flows along the Equator from the date line and south off the coast of Ecuador at Christmas time.
Although El Nino has ended this year, it has caused the warm weather in Pacific Equatorial area and abnormal heat worldwide, he said.
Whatever the causes, these experts agree that they should take various meteorological elements into consideration against the backdrop of climate change, so as to draw a comprehensive conclusion.