Lake Kariba on the Zambezi River border between Zimbabwe and Zambia used to be dotted with hundreds of commercial fishing rigs, while local fishermen in small makeshift boats would catch enough bream for their livelihood.

Now the fishermen are standing on shore praying for rain as drought has shrunk the water level of the world's biggest man-made lake by volume to a record low.

Global warming could make the planet far hotter than currently projected because today's scientific models do not correctly account for the influence of clouds, researchers said this week.

The study in the journal Science was led by researchers at Yale University and Lawrence Livermore National Laboratory.

More than 120 countries have said they are ready to sign the UN's accord to fight global warming, French ecology minister Segolene Royal said Wednesday. 

Venezuelan workers will get Fridays off for the next two months as part of an emergency plan to save electricity, the president said.

Venezuela has the world's largest proven oil reserves but its economy is a mess, with rampant inflation, shortages of goods as basic as soap and toilet paper and constant blackouts.

Almost half of all natural World Heritage Sites, including the Great Barrier Reef and Machu Picchu, are threatened by industrial activities such as mining, oil exploration and illegal logging, conservation group WWF warned Wednesday.

The 114 threatened sites, virtually half the total listed by UNESCO, provide food, water, shelter and medicine to over 11 million people -- more than the population of Portugal, according to a WWF-commissioned report.

The environmental authorities in Mexico City will keep 40 percent of cars off the roads on Wednesday because of extremely high pollution levels, officials said.

"The Greater Capital Area Environmental Commission (CAME) is activating extraordinary measures due to high ozone levels in the metropolitan area of ​​the Valley of Mexico," CAME said in a statement together with city, regional and federal authorities.

Trillions of dollars' worth of financial assets may be under threat from global warming's effects by 2100, climate economists warned on Monday.

Drought-stricken Palau could dry up completely this month, officials warned Monday as the Pacific island appealed for urgent aid from Japan and Taiwan, including shipments of water. 

The tiny country of about 18,000 people declared a state of emergency last month, the latest Pacific island nation to do so as one of the worst ever El Nino-induced droughts in the region worsens. 

New Zealand is renowned for its wondrous scenery, and among the country's top tourist attractions are two glaciers that are stunning and unusual because they snake down from the mountains to a temperate rain forest, making them easy for people to walk up to and view.

But the Fox and Franz Josef glaciers have been melting at such a rapid rate that it has become too dangerous for tourists to hike onto them from the valley floor, ending a tradition that dates back a century. With continuing warm weather this year, there are no signs of a turnaround. Scientists say it is another example of how global warming is impacting the environment.

The United Nations' aid chief for Somalia begged for cash Thursday to stave off starvation amid intense drought affecting a million people and to pull the war-torn country "back from the tipping point."

"Urgent action is required right now. If not, we risk a rapid and deep deterioration of the situation, as drought conditions may worsen in the coming months," UN Humanitarian Coordinator for Somalia Peter de Clercq said, appealing for $105 million (92 million euros) for "life-saving" aid for more than one million people.