David Karoly will rebut the common arguments and misinformation that question the role of human activity, particularly increasing concentrations of atmospheric greenhouse gases, as the main cause of recently observed global warming.
He says, “Recent increases in greenhouse gas concentrations in the atmosphere are due to human activity. The pattern and magnitude of observed global-scale temperature changes since the mid-20th century cannot be explained by natural climate variability. They are consistent with the response to increasing greenhouse gases and aerosols, and are not consistent with the responses to other factors. Hence, it is very likely that increasing greenhouse gases due to human activity are the main cause of the recent observed global-scale warming.”
Further information:
Lies, damn lies and climate change sceptics: What has really caused recent global warming?
David J. Karoly
School of Earth Sciences, The University of Melbourne, VIC 3010, Australia
Abstract summary:
A rebuttal is provided of a number of common arguments and misinformation that question the role of human activity, particularly increasing concentrations of atmospheric greenhouse gases, as the main cause of recent observed global warming.
Abstract:
I. INTRODUCTION
Over the last two decades, there have been thousands of peer-reviewed publications reporting scientific studies o f climate variability and change, leading to understanding of the causes of recent global warming. This understanding is reported in the assessments of the Intergovernmental Panel on Climate Change (IPCC) [1], as well as by the US National Academies [2] and the Australian Academy of Science [3]. They have all reached the same conclusion – the observed increase in global -average surface temperature since the mid- 20th century is mainly due to the increase in greenhouse gases in the atmosphere caused by human activity.
Recently, there has been an increase in opinion pieces in the media and on blogs questioning the scientific understanding of global warming, as well as books such as Heaven+Earth by Ian Plimer [4] and Climate: the Counter Consensus by Bob Carter [5]. The vast majority of scientific studies continue to support and strengthen this conclusion. A common trend among so-called “ global warming skeptics” is to select a small amount of information to support a misleading conclusion. Some of the common misinformation is addressed. The responses are based on peer-reviewed scientific publications and have been collected in a recent report from the Academy of Science [3] and in IPCC assessments. In addition, the specific methods used to quantify the contributions from different forcing factors to recent observed climate change are described.
II. SOME COMMON MISINFORMATION
- Carbon dioxide is such a minor atmospheric constituent that it can’t affect global climate –untrue.
- Increases in carbon dioxide over the last hundred years are due to natural sources – untrue.
- Global-average temperature fell from 2002 to 2008, while carbon dioxide increased, so carbon dioxide can’t cause longterm warming – false conclusion.
- The observed spatial pattern of warming does not show the fingerprint of increasing greenhouse gases – untrue.
- The best explanation for recent global warming is variations of the sun or cosmic rays – untrue.
III. SUMMARY
Recent increases in greenhouse gas concentrations in the atmosphere are due to human activity. The pattern and magnitude of observed global-scale temperature changes since the mid-20th century cannot be explained by natural climate variability, are consistent with the response to increasing greenhouse gases and aerosols, and are not consistent with the responses to other factors. Hence, it is very likely that increasing greenhouse gases due to human activity are the main cause of the recent observed global-scale warming.
REFERENCES
[1] 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, Cambridge, United Kingdom, 2007
[2] Understanding and responding to climate change. National Academies, Washington DC, USA. 24 pp., 2008.
[3] The Science of Climate Change:Questions and Answers. Allison, I., et al., Australian Academy of Science, 16 pp., 2010.
[4] Plimer, I., Heaven+Earth, Connor Court, 503 pp., 2009.
[5] Carter, R. M., Climate: the Counter Consensus, Stacey Intl., 300 pp, 2010
Contact:
David Karoly, dkaroly@unimelb.edu.au