(Bloomberg News) Human behavior is increasing the frequency and severity of natural disasters, according to Jeffrey Sachs, a Columbia University economist.

"I'm not saying Hurricane Irene is an example of that, but I am saying that when you look around the planet, every month you are seeing more shocks, more frequently, more severe than at any time in modern history," Sachs said in a "Bloomberg Surveillance" radio interview with Tom Keene and Ken Prewitt. "We are definitely in the midst of human-made natural disasters."

Hurricane Irene killed at least 40 people as it moved from the Caribbean through New England, left an estimated $2.6 billion in damage and cut power to almost 8 million homes and businesses along the U.S. East Coast. Tropical Storm Katia, about 1,100 miles (1,770 kilometers) from the southernmost Cape Verde Islands, may be declared a hurricane later today, according to the U.S. National Hurricane Center.

"Can one say that Katrina, or Irene or the massive floods in Pakistan or drought in the horn of Africa are examples in that instance of the long-term human induced change?" Sachs said. "That is extremely difficult but on occasion it can be done because the event is so extreme that one can say with a very high assurance that that is human induced -- like the massive heat waves that hit Europe a few years ago."

Prices of raw materials will not spur investors to finding alternatives to commodities that cause climate change, said Sachs, the director of Columbia's Earth Institute and the Quetelet Professor of Sustainable Development at the New York- based university.

'Odd Reality'

"We have the odd reality that we can dig up enough coal or shale gas to wreck the planet before price scarcity itself is going to choke this off," Sachs said. "So we're going to have to make real, conscience choices rather than letting the market itself decide."

The Energy Information Administration, the statistical arm of the U.S. Energy Department, estimates global coal reserves at 909 billion tons, a 129 year supply. Benchmark European coal prices rose 50 cents or 0.4 percent, to $129.50 a metric ton today in London. The five-year average price is $100.48 per metric ton.

"We've transitioned globally into a human-led environment where human's effects on carbon flows, energy flows, water flows are so dominant now that we have changed the probability distribution of when extreme droughts or hurricanes or heat waves are hitting the planet," he said.