MORE INFORMATION- CLIMATE CHANGE

The Broad Evidence for Global Warming

The apparent rise in the Global Mean Temperature over the past 150 years is not the only evidence we have for global warming. Additional evidence compiled by the IPCC’s 2007 report includes increases in ocean temperatures, rising sea levels (Figure 1 (b)) and the widespread melting of snow and ice (Figure 1 (c)).

According to the IPCC 2007:

  • “Observations since 1961 show that the average temperature of the global ocean has increased to depths of at least 3000 m and that the ocean has been absorbing more than 80% of the heat added to the climate system. Such warming causes seawater to expand, contributing to sea level rise.
  • Mountain glaciers and snow cover have declined on average in both hemispheres. Widespread decreases in glaciers and ice caps have contributed to sea level rise (ice caps do not include contributions from the Greenland and Antarctic Ice Sheets).
  • Losses from the ice sheets of Greenland and Antarctica have very likely contributed to sea level rise over 1993 to 2003. Flow speed has increased for some Greenland and Antarctic outlet glaciers, which drain ice from the interior of the ice sheets. The corresponding increased ice sheet mass loss has often followed thinning, reduction or loss of ice shelves or loss of floating glacier tongues.
  • Global average sea level rose at an average rate of 1.8 [1.3 to 2.3] mm per year over 1961 to 2003. The rate was faster over 1993 to 2003: about 3.1 [2.4 to 3.8] mm per year.”

  

Figure 1. Observed changes in (a) global average surface temperature, (b) global average sea level from tide gauge (blue) and satellite (red) data and (c) Northern Hemisphere snow cover for March-April. All changes are relative to corresponding averages for the period 1961–1990. Smoothed curves represent decadal average values while circles show yearly values. The shaded areas are the uncertainty intervals estimated from a comprehensive analysis of known uncertainties (a and b) and from the time series (c). 

(Source:  IPCC 2007 p. 6 )

Scientists from the Australian Climate Change Science Program (a joint program of CSIRO and the Bureau of Meteorology in partnership with the Australian Greenhouse Office) have reported similar findings within the Australian environment:

“Maximum winter snow depth at Spencers Creek in the snowy mountains has decreased slightly since 1962, and the snow depth in spring has declined strongly (by about 40%) …

For the period 1950 to 2000, sea level rose at all of the Australian coastal sites monitored, with substantial variability in trends from location to location. Over the period 1920 to 2000 the estimated average relative sea level rise around Australia was 1.2 mm per year. …

Substantial warming has occurred in the three oceans surrounding Australia. Warming has been large off the south-east coast of Australia and in the Indian Ocean. The tropical Pacific Ocean has warmed over recent decades. Long term observations off Maria Island near Tasmania reveal a warming trend far greater than the global average, and this may be due to changes in the east Australian current … Southern Ocean temperatures have warmed since the 1950s to a depth of 1000 m in some locations.”

(Source: “Climate Change in Australia; Technical report 2007”   pp 53-57).