English: This graph shows two simulations of 20th century global mean temperatures compared with observed temperatures (dotted line). The red line (higher up on the right-hand side graph) shows simulated temperatures including human influences (e.g., greenhouse gases and aerosols), the blue line (lower down on the right-hand side graph) shows simulated temperatures excluding human influences. The graph is adapted from Hegerl et al. (2007) (referred to by the cited source).

From the cited Lindsey (2010) public-domain source: "Reconstructions of global temperature that include greenhouse gas increases and other human influences (red line, based on many models) closely match measured temperatures (dashed line). Those that only include natural influences (blue line, based on many models) show a slight cooling, which has not occurred. The ability of models to generate reasonable histories of global temperature is verified by their response to four 20th-century volcanic eruptions: each eruption caused brief cooling that appeared in observed as well as modeled records." For more information, see attribution of recent climate change.

References:

• Hegerl, G., et al. (2007). Chapter 9: Understanding and attributing climate change. In Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. (Solomon, S., et al., (eds.)), Cambridge University Press.