Managing landscapes for climate-smart agricultural systems:
External forcings include natural phenomena such as volcanic eruptions and variations in the sun's output. Radiative forcing is a measure of how various factors alter the energy balance of the Earth's atmosphere.
Between the start of the Industrial Revolution inand the yearthe increase in the atmospheric concentration of carbon dioxide chemical formula: CO2 led to a positive radiative forcing, averaged over the Earth's surface areaof about 1.
The climate system will vary in response to changes in forcings. This internal variability is a result of complex interactions between components of the climate system, such as the coupling between the atmosphere and ocean see also the later section on Internal climate variability and global warming.
Human factors include the emissions of heat-trapping "greenhouse" gases and particulates as well as clearing of forests and other land-use changes.
Attribution requires demonstrating that a signal is: Key attributions Greenhouse gases Carbon dioxide is the primary greenhouse gas that is contributing to recent climate change.
The Kyoto Protocol lists these together with hydrofluorocarbon HFCsperfluorocarbons PFCsand sulfur hexafluoride SF6 which are entirely artificial gases, as contributors to radiative forcing.
The chart at right attributes anthropogenic greenhouse gas emissions to eight main economic sectors, of which the largest contributors are power stations many of which burn coal or other fossil fuelsindustrial processes, transportation fuels generally fossil fuelsand agricultural by-products mainly methane from enteric fermentation and nitrous oxide from fertilizer use.
However, on a global scale, the concentration of water vapor is controlled by temperature, which influences overall rates of evaporation and precipitation. Between andabout two-thirds of anthropogenic CO2 emissions were produced from burning fossil fuels, and about one-third of emissions from changes in land use,  primarily deforestation.
A second reason that climate change has been attributed to land use is that the terrestrial albedo is often altered by use, which leads to radiative forcing.
This effect is more significant locally than globally. Aerosols produced are primarily black carbon. Over the past years human activities have released increasing quantities of greenhouse gases into the atmosphere. This has led to increases in mean global temperature, or global warming.
Other human effects are relevant—for example, sulphate aerosols are believed to have a cooling effect. Natural factors also contribute. According to the historical temperature record of the last century, the Earth's near-surface air temperature has risen around 0.
The phrase "balance of evidence" suggested the English common-law standard of proof required in civil as opposed to criminal courts: In the Third Assessment Report TAR refined this, saying "There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities".
Evidence of the effect of external influences, both anthropogenic and natural, on the climate system has continued to accumulate since the TAR.
The warming occurred in both the ocean and the atmosphere and took place at a time when natural external forcing factors would likely have produced cooling. Among the possible factors that could produce changes in global mean temperature are internal variability of the climate system, external forcing, an increase in concentration of greenhouse gases, or any combination of these.
Current studies indicate that the increase in greenhouse gases, most notably CO2, is mostly responsible for the observed warming. Evidence for this conclusion includes: Estimates of internal variability from climate models, and reconstructions of past temperatures, indicate that the warming is unlikely to be entirely natural.
Climate models forced by natural factors and increased greenhouse gases and aerosols reproduce the observed global temperature changes; those forced by natural factors alone do not.
This conclusion rests on multiple lines of evidence. Like the warming "signal" that has gradually emerged from the "noise" of natural climate variability, the scientific evidence for a human influence on global climate has accumulated over the past several decades, from many hundreds of studies.
No single study is a " smoking gun.Get the latest international news and world events from Asia, Europe, the Middle East, and more. See world news photos and videos at urbanagricultureinitiative.com Half of the world's wetlands were lost last century. Logging and conversion have shrunk the world's forests by as much as half.
Some 9 percent of the world's tree species are at risk of extinction; tropical deforestation may exceed , square kilometers per year.
proximate drivers responsible for deforestation. If suitable maps and spatial data are not available, remote sensing analysis must be conducted by a member of the driver assessment team familiar with.
responsible and sustainable production of biofuels can be only, reference for discussion and analysis of forest and deforestation data at regional and global level.
However, the FAO that underlying economic factors are prominent driving forces for tropical . analysis of deforestation environment and sustainable development according to available environment and economic development this collection of essays analyzes the forces responsible for deforestation the governmental policies that effect this destruction and the roles.
“Community forest management linked to responsible markets is key to conserving forests, biodiversity, and environmental services,” Edgar González Godoy, Rainforest Alliance director for Mexico, said.