As 2013 comes to a close, a review of the key climate events of the year reveals some interesting new research and effective myth debunking, but little net progress in terms of addressing the problem through policies to reduce greenhouse gas emissions.
Beginning with the good news, the myth of the global warming ‘pause’ – which has helped policymakers justify delaying action to address climate change – was thoroughly debunked in 2013. A paper published by Kevin Cowtan and Robert Way showed that, in addition to the myth being a clear case of cherry picking short-term noise in the data, global surface temperatures have actually risen about two and a half times faster over the past 15 years than previously estimated. The short-term ‘pause’ was mostly an artifact resulting from a lack of temperature station coverage in the Arctic, where global warming is happening fastest.
Skeptical Science also released a new global warming widget showing that when accounting for the entire global climate, the planet has been accumulating over 4 Hiroshima atomic bomb detonations worth of energy per second, and over 2 billion detonations worth of heat since 1998.
Several other papers this year helped to investigate the cause of the slight slowing in the warming of global surface temperatures. Kosaka & Xie (2013) showed that changes in the Pacific Ocean could account for most of the short-term global surface temperature changes. Along those lines, Watanabe et al. (2013) showed that ocean heat uptake has become more efficient over the past decade, which is consistent with the observations of Balmaseda et al. (2013), who found an unprecedented transfer of heat to the deep oceans over the past decade, consistent with the modeling in Meehl et al (2013).
Putting it all together, we have an increasingly clear picture that while the warming of global surface temperatures has slowed over the past decade, it has not slowed as much as previously thought. The slowed surface warming is due in large part to changes in ocean cycles, particularly in the Pacific Ocean, causing more efficient ocean heat uptake, thus leaving less heat to warm surface temperatures. External factors, like decreased solar and increased volcanic activity, have also played a role in the slowed surface warming, but internal variability due to ocean cycles appears to be the main culprit. In any case, as the 2013 IPCC Fifth Assessment Report showed, the observed global surface warming remains within the range of climate model projections.