Abstract

A perspective is given on human-induced climate change, contrasting two complementary approaches. The first is the conventional approach of using climate models as a means for developing understanding of the climate system variations and for projections of the future. Climate models have improved... Show moreA perspective is given on human-induced climate change, contrasting two complementary approaches. The first is the conventional approach of using climate models as a means for developing understanding of the climate system variations and for projections of the future. Climate models have improved enormously, but even with the biggest supercomputers, models cannot resolve scales needed to depict many important phenomena. Major challenges remain in addressing chaotic natural weather and climate variability, and processing huge volumes of data. The second is an approach based upon understanding the changing Earth's energy imbalance (EEI) and tracking the consequences through the flows of energy through the climate system. A new assessment is given of the EEI through estimates of the uptake of heat by glaciers and ice sheets, land, and the oceans, and implications for the hydrological cycle. The oceans take up 93% of EEI of 0.9 +/- 0.2 W m(-2) (or 430 TW). Climate change is already readily apparent, with major consequences and costs. Show less