During the second half of the twentieth century, the West Antarctic Ice Sheet (WAIS) has undergone significant warming at more than twice the global mean and thus is regarded as one of the most rapidly warming regions on Earth. However, a reversal of this trend was observed in the 1990s, resulting in regional cooling. In particular, during 1999–2018, the observed annual average surface air temperature had decreased at a statistically significant rate, with the strongest cooling in austral spring.
From NoTricksZone
By Kenneth Richard on 6. November 2023
Significant 21st century cooling in the Central Pacific, Eastern Pacific, and nearly all of Antarctica “implies substantial uncertainties in future temperature projections of CMIP6 models.” – Zhang et al., 2023
New research indicates West Antarctica’s mean annual surface temperatures cooled by more than -1.8°C (-0.93°C per decade) from 1999-2018. In spring, the West Antarctic Ice Sheet (WAIS) cooling rate reached -1.84°C per decade.
Not only has the WAIS undergone significant cooling in the last two decades, most of the continent also cooled by more than 1°C. See, for example, the ~1°C per decade cooling trend for East Antarctica (2000 to 2018) shown in Fig. ES1.
Of 28 CMIP6 models, none captured a cooling trend – especially of this amplitude – for this region. This modeling failure “implies substantial uncertainties in future temperature projections of CMIP6 models.”
The post-1999 cooling trend has not just been confined to Antarctica. Sea surface temperatures (SSTs) in the Eastern and Central Pacific (south of 25°N) also cooled from 1999-2018 relative to 1979-1997. This cooling encompasses nearly half of the Southern Hemisphere’s SSTs.
The 1999-2018 mean annual surface temperature cooling of the Antarctic continent and nearly half of the Southern Hemisphere’s SSTs do not support the claims that surface warming is driven by human emissions of greenhouse gases (GHGs). After all, if the widespread cooling cannot be explained by the increase in GHG forcing, why would the same concentrations of GHGs explain the areas with warming temperatures?
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