Earth energy for the greenhouse effect, life on Earth would not exist. The Sun emits radiation to the Earth. If we could imagine a flat surface at the top of the atmosphere, that radiation is about 340 watts per square meter (340 W/m- 2). Earth’s surface, leaving some 240 W/m-2 that heats up the surface of the Earth.Incoming solar radiation: + 340 W Outgoing radiation: - 420 W m-2m-2 Greenhouse effect: + 180 W m-2Reflected from clouds, the Earth’s Net outgoing (thermal) radiationsurface, etc.: - 100 W m-2
The greenhouse effect is a good thing life on Earth. The problem arises Because humankind is Adding to the effect by increasing the amounts of CO2 and a f in theatmosphere, notably methane (CH4) and nitrous oxide (N2O).
The next issue is to predict what would happen if thesetemperature changes were allowed to happen. The science ofclimate change impact assessment is very uncertain, not leastbecause humans have the capacity to adapt to some of theexpected changes. There are two stages to impact assessment:predicting what the consequences will be for ecosystem changeand human health, and assessing how important those changeswill be.Even more speculative are the effects of extreme events: forexample, the worsening of El Niño, reserved.Ecosystems change in response to climate change but, ingeneral, past changes have occurred slowly as temperaturesvaried over long periods. A rise of 1 or 2° C in just a century is avery fast rate of temperature change, and some ecosystems maynot be able to adjust
Listing possible impacts is one thing; saying how important theyare is another. Yet some idea of the collective magnitude of theimpacts is essential because the measures needed to reduce ratesof warming will not be cheap. Economic studies suggest a fairlyuniform measure of damage of about 1 to 2 per cent of the world’sentire economic output. But this is a figure relating to “2 xCO2”, that is, for a doubling of CO2 concentrations in theatmosphere. It is a benchmark widely used for economic andscientific analysis, but global US$30 perwill not stop there ifThis figure is probably around warming tone, but with a fairlyunchecked, so uncertainty surrounding itfar future could be verywide range of the damages in the very .much higher.As with virtually all aspects of the global warming debate, thereare many complications. First, it seems likely that the costs ofcontrolling carbon emissions now is fairly low for the firsttranche of emissions, but as more and more reduction occurs itwill become increasingly expensive to reduce emissions.
These widely varying views also explain the differences of opinionabout the adequacy of the actions already taken. It does notbenefit any single nation to take action unless it can be assuredothers will act likewise. The disadvantages of being a “firstmover” explain why the subject has to be dealt with at theinternational level, initially through the United Nations FrameworkConvention on Climate Change (UNFCCC) in 1992 in Rio deJaneiro, and subsequently at the Conference of Parties in Kyoto in1997. The Kyoto Protocol, which emerged from the 1997conference and came into force in February 2005, is the firstagreement under the UNFCCC with greenhouse gas emissionreduction targets that is binding in international law. The UNFCCCitself set voluntary targets for industrialized nations such that theirCO2 emissions should be no higher in 2000 than they were in1990. Developing countries argued that they had no