Source: http://www.eere.energy.gov/news/news_detail.cfm/news_id=12585

A new interagency federal report finds that climate change is
already having visible impacts in the United States and could
threaten many sectors of the economy, including agriculture.
A series of similar reports document the current global effects
of climate change, including more than 300,000 deaths per
year and economic losses of $125 billion per year.