TABLE 1.2 List of Observed Impacts Attributed to Global Warming by IPCC AR4 WG2 with Results from Two Studies Using Formal D&A Methodology

Driving Change in Physical Climate



Changing snow/ice/frozen ground

Increase in number and extension of glacial lakes, increase in avalanches and instability of permafrost, and changes in polar ecosystems

IPCC AR4 WG2 (IPCC, 2007b)

Warmer temperatures

Increase in runoff and anticipated snow melt in spring; increase in temperatures in lakes and rivers

IPCC AR4 WG2 (IPCC, 2007b)

Warmer temperatures

Earlier timing of spring event (foliage, migrations, and egg-laying) and range shifts (poleward and upward) of terrestrial biological systems

IPCC AR4 WG2 (IPCC, 2007b)

Rising ocean water temperatures/changes in ice cover, salinity, oxygen levels, and circulation

Shifts in the ranges of algae/plankton/fish abundance in high-latitude oceans and high-latitude/high-elevation lakes

IPCC AR4 WG2 (IPCC, 2007b)

Increase in atmospheric concentration of CO2

Ocean acidification (no effect on ocean life documented yet

IPCC AR4 WG2 (IPCC, 2007b)

Summer temperature warming in Canada

Increase in area burned by forest fires in Canada

Gillett et al., 2004

Increase in temperature

Increase in growing season length

Christidis et al., 2007

NOTE: Confidence levels are not available because the IPCC AR4 WG2 did not supply them.

positive spatial correlation between said impacts and regionally differentiated warming.

This reasoning is at the basis of the list of impacts attributed to global warming by IPCC AR4 WG2 in its Summary for Policy Makers, which we list, together with results from two studies that applied formal D&A methodology,2 in Table 1.2.


Of these two studies, the first is reviewed by WG,2 but its results are not explicitly listed in its Summary for Policy Makers, SPM; the second appeared later than the release of the report.

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