The White House says first lady Michelle Obama's guests for the State of the Union address Tuesday evening include two Arizonans : Avondale Mayor Marie Lopez Rogers and 12-year-old Haile Thomas of Tucson.

Arizona is formally withdrawing from the Western Climate Initiative, a regional collaboration to establish a cap-and-trade program to reduce emissions of greenhouse gases.

A new government report says already scarce water supplies in the Western United States are likely to dwindle further as a result of climate change, exacerbating problems for millions of water users in the West.

Officials with the Coconino National Forest are rewriting a 23-year-old blueprint for the forest and attempting to address some big problems, like climate change and water pollution.

The safety and security of the United States will depend on how well we as a nation address the challenges of climate change.

The desert tortoise thrives in intense heat and can go a year without water, but it's among the species threatened by climate change, an wildlife group says. Looking toward events Oct. 24 calling attention to carbon emissions and their role in warming the planet, the Tucson-based Center for Biological Diversity released a report highlighting 350 animal and plant species it says could vanish due to climate change. Of those, 24 are Arizona locals.

A new study suggesting that human activities are nearing or exceeding the boundaries of Earth's ability to sustain life as we know it has special significance in the Southwest, which is especially vulnerable to the effects of climate change, two Arizona researchers who served as co-authors said Sept. 24.