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Observed temperature changes
The Earth's average surface temperature rose by 0.74±0.18 °C over the period 1906–2005.
The rate of warming over the last half of that period was almost double
Greenhouse gasesThe greenhouse effect is a process by which thermal
radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all
directions.
Con…Naturally occurring amounts of greenhouse gases have a mean warming
effect of about 33 °C (59 °F).The major greenhouse gases are Water vapor, which causes about 36–70% of the greenhouse effect Carbon dioxide (CO2), which causes 9–26% Methane (CH4), which causes 4–9%; and Ozone (O3), which causes 3–7%.
Observed and expected environmental effects
Detection and attribution may also be applied to observed changes in physical, ecological and social systems.
Natural systemsGlobal warming has been detected in a number of natural
systems. e.g. sea level rise and widespread decreases in snow and ice extent.
Ecological systemsclimate change is expected to particularly affect certain
ecosystems, including tundra, mangroves, and coral reefs. Dissolved CO2 increases ocean acidity.
Observed and expected effects on social systems
Food security- Under present trends, by 2030, decrease by up to 30% while rice, millet and maize in South Asia could decrease by up to 10%.
Habitat inundation- Maldives, Tuvalu and homelessness in countries with low lying areas such asBangladesh
Responses to global warming Mitigation : The IPCC defines mitigation as activities that reduce
greenhouse gas (GHG) emissions. Many countries, both developing and developed, are aiming to use cleaner, less polluting, technologies.
Energy-related carbon-dioxide (CO2) emissions in 2010 were the highest in history, breaking the prior record set in 2008.
CON… Adaptation : A concept related to adaptation is "adaptive
capacity," which is the ability of a system (human, natural or managed) to adjust to climate change
CON… Geoengineering : Geoengineering, the deliberate modification of
the climate, has been investigated as a possible response to global warming, e.g. by NASA and the Royal Society