See the trend in hot days in these U.S. cities.
A small increase in average temperature leads to a big increase in extreme heat.
Warming waters are decreasing oxygen in the oceans, creating dead zones for marine plants and animals.
Excessive carbon emissions are worsening the ocean's health.
Here's how the decline in coal use is linked to climate-friendly cars.
Here's what makes a car climate friendly.
The first day with summer-like temperatures is happening earlier for most of these cities.
The amount of carbon dioxide in the atmosphere has a strong correlation with rising temperatures.