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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

What the science says...

Once natural influences, in particular the impact of El Niño and La Niña, are removed from the recent termperature record, there is no evidence of a significant change in the human contribution to climate change.

Global temperatures are affected by both natural and human factors. The human influence is dominated by a slow but inexorable warming caused by greenhouse gas emissions. Natural factors include strong but short lived changes due to El Niño, La Niña and volcanoes.

In order to reliably measure the human influence on climate it is necessary either to use temperature data covering several decades, or to first remove the effect of the natural influences. Both approaches give the same result - human activity is warming the planet.

A media myth has emerged disputing this fact. The myth is based on the fact that temperatures have risen more slowly over the past 16 years than previously. However this period is too short to eliminate the effect of short term natural influences on temperature, and no other attempt has been made to eliminate their effect. Therefore the conclusion is invalid.

The ‘16years’ video demonstrates how the natural influences are removed from the temperature record, and that the rate of warming due to human activity shows essentially no change.

In order to address the audience of the media myths the language in the video has necessarily been heavily simplified. Additional information is provided in the video description and in the advanced version of this rebuttal.

Implications

The 16-year temperature trend provides no evidence to suggest that human-caused greenhouse warming has slowed.

The 16-year temperature trend provides no evidence to suggest that the consensus understanding of human-caused climate change is incorrect.

Given that human greenhouse gas emissions are increasing, and that the natural influences do not show a trend on longer timescales, we must expect increasing global warming in the future.

References

Foster and Rahmstorf (2011), Global temperature evolution 1979–2010 doi:10.1088/1748-9326/6/4/044022

Rypdal (2012) Global temperature response to radiative forcing: Solar cycle versus volcanic eruptions doi:10.1029/2011JD017283

Nuccitelli et al. (2012) Comment on Ocean heat content and Earth's radiation imbalance. II. Relation to climate shifts doi:10.1016/j.physleta.2012.10.010

Updated on 2013-01-09 by Kevin C.

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