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The link between extreme weather events, climate change, and national security is discussed in Extreme Realities, a new episode in PBS’ series Journey To Planet Earth hosted by Matt Damon.
The video features a number of extreme weather phenomena: hurricanes, tornadoes, floods, wild fires, and flooding. The discussion is about climate change and the consequences on the ground – or, how climate change may affect you.
It is important to ask what is the story behind the assertions made in the video. What scientific support is there for the link between such extremes and climate change?
The recent warming has been more pronounced in the Arctic Eurasia than in many other regions on our planet, but Franzke (2012) argues that only one out of 109 temperature records from this region exhibits a significant warming trend. I think that his conclusions were based on misguided analyses.
The analysis did not sufficiently distinguish between signal and noise, and mistaking noise for signal will give misguided conclusions.
C. Franzke, "On the statistical significance of surface air temperature trends in the Eurasian Arctic region", Geophysical Research Letters, vol. 39, pp. n/a-n/a, 2012. http://dx.doi.org/10.1029/2012GL054244
A number of blogs were excited after having leaked the second-order draft of IPCC document, which they interpreted as a “game-changing admission of enhanced solar forcing”.
However, little evidence remains for a link between galactic cosmic rays (GCR) and variations in Earth’s cloudiness. Laken et al. (2012) recently provided an extensive review of the study of the GCR and Earth’s climate, from the initial work by Ney (1959) to the latest findings from 2012.
B.A. Laken, E. Pallé, J. Čalogović, and E.M. Dunne, "A cosmic ray-climate link and cloud observations", J. Space Weather Space Clim., vol. 2, pp. A18, 2012. http://dx.doi.org/10.1051/swsc/2012018
A new paper by Deser et al. (2012) (free access) is likely to have repercussions on discussions of local climate change adaptation. I think it caught some people by surprise, even if the results perhaps should not be so surprising. The range of possible local and regional climate outcomes may turn out to be larger than expected for regions such as North America and Europe.
Deser et al. imply that information about the future regional climate is more blurred than previously anticipated because of large-scale atmospheric flow responsible for variations in regional climates. They found that regional temperatures and precipitation for the next 50 years may be less predictable due to the chaotic nature of the large-scale atmospheric flow. This has implications for climate change downscaling and climate change adaptation, and suggests a need to anticipate a wider range of situations in climate risk analyses.
Although it has long been recognised that large-scale circulation regimes affect seasonal, inter-annual climate, and decadal variations, the expectations have been that anthropogenic climate changes will dominate on time scales longer than 50 years. For instance, an influential analysis by Hawking & Sutton (2009) (link to figures) has suggested that internal climate variability account for only about 20% of the variance over the British isles on a 50-year time scale.
C. Deser, R. Knutti, S. Solomon, and A.S. Phillips, "Communication of the role of natural variability in future North American climate", Nature Climate change, vol. 2, pp. 775-779, 2012. http://dx.doi.org/10.1038/nclimate1562
E. Hawkins, and R. Sutton, "The Potential to Narrow Uncertainty in Regional Climate Predictions", Bulletin of the American Meteorological Society, vol. 90, pp. 1095-1107, 2009. http://dx.doi.org/10.1175/2009BAMS2607.1
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