On Antarctica And Thelarsenb Ice Shelf

Lomborg's main points about Antarctica in Cool It are that the Antarctic continent has cooled in the past several decades, that the dramatic warming of the Antarctic Peninsula is not unprecedented within the past several thousand years, and that Antarctica's contribution to sea-level rise this century will be minimal. 1

To support his assertion that the Antarctic continent has cooled, Lomborg cited three sources, none of which had been published in a peer-reviewed journal as of Cool It's publication date. 2 Lomborg's first source was a draft paper, "A Synthesis of Antarctic Temperatures," that, as the draft noted, was submitted for publication in 2005. Though the paper was published (Chapman and Walsh, 2007) too late for Lomborg to cite in Cool It, I will refer to both its unpublished and published versions.

Contrary to what Lomborg reported — that the Antarctic continent has cooled—the published study by Chapman and Walsh reported that much of the Antarctic continent had slightly warmed for much of the recent past, though the authors reported they could detect no significant overall trend: "Trends calculated for the 19582002 period suggest modest warming over much of the 60°-90°S domain. All seasons show warming.. Because of the large inter-annual variability of temperatures over the continental Antarctic, most of the continental trends are not statistically significant."

The published draft of the Chapman and Walsh paper thus did not say definitively that the Antarctic continent had cooled; if anything, it reported that the continent had experienced a modest overall warming trend from 1958 to 2002. In addition, the unpublished draft — the one that Lomborg did cite — also reported a "modest warming" on the continent: "Trends calculated for the 1958-2002 period show modest warming over much of 50-90°S with maximum warming over the Antarctic Peninsula."4

Furthermore, the unpublished draft appeared to link a detectable warming trend in Antarctica to global warming— enough so that it seemed to undermine Lomborg's assertion that continental Antarctica has cooled and was thus not susceptible to the effects of global warming: "Composite (11-model) GCM-simulations for 1958-2002 with forcing from historic greenhouse gas concentrations show warming patterns and magnitudes similar to the corresponding observed trends.5" Overall, neither the published nor the unpublished draft of the Chapman and Walsh study supported Lomborg's claim that the Antarctic continent had undergone a definable cooling; in fact, much of the reported data was to the contrary.

The second source that Lomborg cited to support his claim that the Antarctic continent has cooled was a paper posted by a scientist on the Internet; it did not appear to be a published peer-reviewed study.6 And the third source could not be located using the Lomborg-provided URL.

Two studies, led by Andrew Monaghan of Ohio State University and published soon after the 2007 publication date of Cool It, also did not support Lomborg's claim. One, published in 2008 in the Bulletin of the American Meteorological Society, reported "statistically insignificant seasonal and annual near-surface temperature changes over continental Antarctica from the late 1950s through 2000." 8 The second, published in the Journal of Geophysical Research in 2008, reported "widespread but statistically insignificant warming over Antarctica from 1992-2005." 9 Indeed, after these reports of statistically insignificant temperature trends, a study published in Nature Geoscience (Gillett et al., 2008) reported that Antarctica had significantly warmed, and that the warming was caused by human-induced climate change: "We find that the observed changes in Arctic and Antarctic temperatures are not consistent with internal climate variability or natural climate drivers alone, and are directly attributable to human influence. Our results demonstrate that human activities have already caused significant warming in both polar regions, with likely impacts on polar biology, indigenous communities, ice-sheet mass balance and global sea level." 10

Another paper (Schneider and Steig, 2008), published in the Proceedings of the National Academy of Sciences, reconstructed temperatures over West

Antarctica using ice cores, and reported that statistically significant warming had occurred over the Western Antarctic ice sheet during the twentieth century, "underscoring the sensitivity of West Antarctica's climate, and potentially its ice sheet, to large-scale changes in the global climate." 11 A short time later, a major study (Steig et al., 2009), published in Nature, reported: "We show that significant warming extends well beyond the Antarctic Peninsula to cover most of West Antarctica, an area of warming much larger than previously reported. West Antarctic warming exceeds 0.1°C per decade over the past 50 years, and is strongest in winter and spring. Although this is partly offset by autumn cooling in East Antarctica, the continent-wide average near-surface

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