Blue is Natural, forced by changes in solar irradiance and volcanic aerosols. Figures 3-5 show evidence of a global warming signal in the cryospheric and oceanic environments. Observed and modeled variations of annual average of NH sea ice extent. The modeled data are from the GFDL and Hadley Centre climate model runs forced by GHGs and aerosols. Glacier mass balance for the years 1988-1998.
Blue circles indicate positive, and red circles negative, balances.
An estimate of glacier change over the last decade based on variations of mountain glacier snowlines is depicted in Figure 4. On a global basis, the predominant trend has been retreat, with the exception of Norway where there have been compensating increases in precipitation. Figure 5 shows the variation in the heat content of the world ocean from the surface to a depth of 3000m. The Atlantic and Pacific Oceans have undergone a net warming from the 1950s and the Indian Ocean has warmed since the mid-1960s. We need to understand it more fully so that we can avoid surprises and intelligently react to changes.