Report: Human-caused climate change exacerbates extreme weather

SAN FRANCISCO-- Government scientists said Thursday that 14 of last year's extreme weather events were made worse by climate change caused by pollution -- examples include the 2014 California wildfires, and cyclones in Hawaii.

In a recent development, California continues to feel the effects of climate change. Most years the Dungeness crab harvest in California is bountiful and worth close to $60 million, but this year there may not be any harvest. High levels of toxic algae in the ocean make the crab too dangerous to eat. The widespread algae bloom is because of unusually high temperatures in the Pacific.

"It's unbelievably warm. We have never had a warming event like this -- the extent of it, the different contributing factors, and how this going to play out this season leads scientists to have huge concerns," said Sarah Cohen who is a marine biologist at San Francisco State University.

Extreme heat events are one focus of the report on the impact of climate change around the world. The study found that in 2014, extreme heat waves, like one that gripped South Korea, were made worse by human-caused climate change which includes things such as car emissions, burning coal and methane gas.

The report studied 28 extreme weather events around the world last year. Fourteen of those -- including devastating floods in Australia and New Zealand -- were found to be made worse in part by climate change.

But the impact of human activity can be complex, the report says. In the United States, record snowfall in the Northeast and Midwest was not a result of climate change -- rather, just cyclical weather patterns.

However, the study says severe wildfires in California are becoming more likely because of global warming.

"Climate change is causing a lot of unfortunate, disastrous impacts around the world," Cohen said.

This is the 4th year scientists have studied whether human activity is at least partially to blame for such things as heat waves, droughts, and wildfires. Over those years, more than half the extreme weather events studied have been linked to human-caused climate change

  • John Blackstone

    From his base in San Francisco, CBS News correspondent John Blackstone covers breaking stories throughout the West. That often means he is on the scene of wildfires, earthquakes, floods, hurricanes and rumbling volcanoes. He also reports on the high-tech industry in Silicon Valley and on social and economic trends that frequently begin in the West.