The effects of global warming are the environmental and social changes caused (directly or indirectly) by human emissions of greenhouse gases. There is a scientific cobsensus that climate change is occuring, and that human activities are the primary driver.Many impacts of climate change have already been observed, including glacier retreat changes in the timing of seasonal events(e.g., earlier flowering of plants),and changes in agricultural productivity.
Future effects of climate change will vary depending on climate change policy and social development.
The two main policies to address climate change are reducing human greenhouse gas emissions and adapting to the impact of climate change. Geoengeneeringis another policy option.
Near-term climate change policies could significantly affect long-term climate change impacts.Stringent mitigation policies might be able to limit global warming (in 2100) to around 2 degree celcious or below, relative to pre-industrial levels. Without mitigation, increased energy demand and extensive use of fossil fuel might lead to global warming of around 4 °C.Higher magnitudes of global warming would be more difficult to adapt to,and would increase the risk of negative impacts.
