FIGURE 2.1 Global surface temperature change from 1880 to 2010, reported as a deviation from the 1951-1980 average. The black curve shows the globally and annually averaged near-surface temperature derived from a variety of instruments including thermometers, satellites, and various ocean sensors, all carefully calibrated and quality-controlled to remove errors. Green bars indicate the 95 percent confidence interval. The red curve shows a five year running average. The data show considerable year-to-year and decade-to-decade variability, but the long-term trend is clearly one of warming. SOURCE: NASA/ GISS (other research groups find similar results; see, for example, temperature/).

  • Both basic physical principles and sophisticated models of the Earth’s climate system definitively show that when the GHG concentrations increase, warming will occur.
  • Careful analyses of observations and model results indicate that natural factors such as internal climate variability or changes in incoming energy from the sun cannot explain the long-term global warming trend.12 Natural climate variability does, however, lead to substantial year-to-year and decade-to-decade fluctuations in temperature and other climate variables (as evident in Figure 2.1).

Global warming has been accompanied by a number of other global and regional environmental changes, which are broadly consistent with the changes expected in a warming world. However, establishing a direct, empirically-based causal link between

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