Hungry microbes feasting on spilled BP oil caused a drop in oxygen levels in the Gulf of Mexico, but did not create a marine “dead zone” near the wellhead, U.S. scientists reported on Tuesday. The amount of oxygen decreased by 20 percent from the long-term average in areas where oil from the broken BP Macondo wellhead was detected by government and independent observers, scientists from the National Oceanic and Atmospheric Administration told reporters. “All the scientists working in the Gulf have been carefully watching dissolved oxygen levels because excess carbon in the system might lead to a dead zone,” said NOAA’s Steve Murawski. “While we saw a decrease in oxygen, we are not seeing a continued downward trend over time.”

Melting glaciers, more humid air and eight other key indicators show that global warming is undeniable, scientists said on Wednesday, citing a new comprehensive review of the last decade of climate data. Without addressing why this is happening, the researchers said there was no doubt that every decade on Earth since the 1980s has been hotter than the previous one, and that the planet has been warming for the last half-century. This confirms the findings of the U.N. Intergovernmental Panel on Climate Change, which reported in 2007 with 90 percent certainty that climate change is occurring. The IPCC also said that human activities contribute to this phenomenon. The new report was released after U.S. Senate Democrats delayed any possible legislation to curb climate change until September at the earliest. Prospects for U.S. climate change legislation this year are considered slim.

Seventy percent of firms with revenue of $1 billion or more say they plan to increase spending on climate change initiatives in the next two years, a global survey reported on Tuesday. Nearly half of the 300 corporate executives who responded to a survey conducted for the accounting and consulting giant Ernst & Young said their climate change investments will range from 0.5 percent to more than 5 percent of revenues by 2012. More than four out of five respondents, or 82 percent, said they plan to invest in energy efficiency in the next 12 months, with 92 percent saying energy costs will be an important driver over that period.