1. This article is about the effects of global
warming and climate change. The effects, or
impacts, of climate change may be physical,
ecological, social or economic. Evidence of
observed climate change includes the
instrumental temperature record, rising sea
levels, and decreased snow cover in the
Northern Hemisphere

2. According to IPCC (2007a:10), "[most] of the observed increase in
global average temperatures since the mid-20th century is very likely
due to the observed increase in [human greenhouse gas]
concentrations". It is predicted that future climate changes will include
further global warming (i.e., an upward trend in global mean
temperature), sea level rise, and a probable increase in the frequency of
some extreme weather events. Signatories of the United Nations
Framework Convention on Climate Change have agreed to implement
policies designed to reduce their emissions of greenhouse gases.

3. This section describes some physical impacts of climate
change. For some of these physical impacts, their effect on
social and economic
systems are also described.

4. Effects on weather
Increasing temperature is likely to lead to increasing
precipitation but the effects on storms are less clear.
Extra tropical storms partly depend on the temperature
gradient, which is predicted to weaken in the northern
hemisphere as the polar region warms more than the
rest of the hemisphere.