The temperature has recently dropped more than half a degree C due mostly to cooler surface sea temperatures. It is estimated that the next couple of years will be cooler until the hotter side of the cycle combines with elevated atmospheric greenhouse gas to cause record high surface air temperatures. Ecosystems are sensitive to temperature increase: “Leemans and Eickhout (2004) found that adaptive capacity decreases rapidly with an increasing rate of climate change. Their study finds that five percent of all ecosystems cannot adapt more quickly than 0.1 C per decade over time. Forests will be among the ecosystems to experience problems first because their ability to migrate to stay within the climate zone they are adapted to is limited.
If the rate is 0.3 C per decade, 15 percent of ecosystems will not be able to adapt. If the rate should exceed 0.4 C per decade, all ecosystems will be quickly destroyed, opportunistic species will dominate, and the breakdown of biological material will lead to even greater emissions of CO2. This will in turn increase the rate of warming”
Leemans og Eickhout, 2004, Another reason for concern: regional and global impacts on ecosystems for different levels of climate change, Global Environmental Change 14, 219–228. The extra heat from the greenhouse gas already in the air is almost 3 Watts per square meter. Elevated levels of CO2 will cause the surface temperature to rise for half a century (for instance 3W of forcing means about a 2C rise in temperature by mid-century). If the rate should exceed 0.4 C per decade, then all ecosystems are quickly destroyed, and there is probably almost enough extra greenhouse gas in the air now to guarantee that temperature increase.
When the ecosystems collapse the carrying capacity of the Earth will quickly lower, causing civil unrest and war, "There is no linear predictability in terms of how ecosystems respond. The phenomena of collapse is one that we have under-appreciated, partly because of the feed-back mechanisms that we are still trying to understand." Achim Steiner, head of the UN Environment Programme, Oct. '07 Please don’t point to the recent decrease in temperature to argue that global warming doesn’t exist, or prescribe emission cuts to solve it. Our current warming commitment practically guarantees abrupt climate change and runaway global warming. We need to remove the excess CO2 from air to make up for past emissions and inevitable future ones.
Unfortunately, there isn’t enough time to avoid ecosystem collapse, particularly as nature will be removing less CO2 from the air as carbon sinks become saturated, and emitting more as the carbon sinks become carbon emitters as it warms. There is a very inexpensive simple way to immediately cool the Earth: just put a small amount of aerosol into the air to dim the sun. We may not be able to stop global warming without geoengineering: capturing and burying just 10 percent of the CO2 emitted from coal-fired plants would require moving more volume of compressed CO2 than the entire annual flow of oil worldwide. Such an enormous engineering challenge would require decades and trillions of dollars.
"I'm going to tell you something I probably shouldn't: we may not be able to stop global warming. We need to begin curbing global greenhouse emissions right now, but more than a decade after the signing of the Kyoto Protocol, the world has utterly failed to do so. Unless the geopolitics of global warming change soon, the Hail Mary pass of geoengineering might become our best shot." --Bryan Walsh, Time Magazine, 17 March 2008