Average Temperature of the Northern Hemisphere based on published research. The black line at the right is instrumental data recorded since 1856; follow the link to see the other sources. Figure created by Robert A. Rohde and distributed under a Creative Commons License.
Today representatives from numerous countries and organizations are starting a conference in Copenhagen to discuss the changing climate. The meeting was intended to produce a new international treaty to replace the Kyoto Protocols from 1998. Whether such a treaty will be signed this month remains to be seen; some news reports have indicated that negotiations might continue into early next year.
Even if a treaty is signed, it is likely to result in lower emissions reductions than needed. The scientific consensus appears to be that the highest atmospheric carbon levels that the climate can tolerate without triggering catastrophic change is about 350 parts per million. Even that level would trigger some rather uncomfortable effects. Since we are already above that level, emissions need to be cut deeply rather than just stabilized. Most accounts I have read suggest cutting global carbon emissions 80% by 2050, with a somewhat lesser goal by 2020. In the past few months, Obama has suggested cutting U.S. emissions 4% by 2020 (with more cuts later), while European leaders offer a 20% cut (3o% if the U.S. agrees to do it to) by 2020.
To some extent, making a smaller cut now could start the ball rolling towards deeper cuts later. However, this present an element of risk. To date, temperature changes have tended to match the worst case forecasts presented by the IPCC. If that trend continues, even faster and deeper cuts may be necessary to forestall catastrophic changes. Our governments really ought to make a serious start now.