The Earth's climate is changing. Temperatures are rising, snow and
rainfall patterns are shifting, and more extreme climate events – like
heavy rainstorms and record high temperatures – are already taking
place. Scientists are highly confident that many of these observed
changes can be linked to the climbing levels of carbon dioxide and other
greenhouse gases in our atmosphere, which are caused by human
activities.
The climate change indicators in this report look at the composition
of the atmosphere, fundamental measures of climate, and the extent to
which several climate-sensitive aspects of the oceans, snow and ice,
human health, society, and ecosystems are changing. Together, these
indicators present compelling evidence that climate change is happening
now in the United States and around the world.