New research published yesterday, 11/28/2012, in IOP Publishing’s journal Environmental Research Letters, reports that sea levels are actually rising at a rate of 3.2 mm a year compared to the best estimate of 2 mm a year in the Intergovernmental Panel on Climate Change’s (IPCC) fourth assessment report (AR4).
The study’s focus was to analyze global temperature and sea level data for the past two decades and compare them to climate projections made in the IPCC’s AR3 and AR4. The authors denote that the present overall global warming trend of 0.16°C per decade matches well with the best estimates of the IPCC, particularly if short-term variable effects of events such as El Nino-Southern Oscillation, solar variability, and volcanic activity are taken into consideration.
Sea level rise, based upon satellite altimeter measurements, however, differs greatly from the IPCC’s AR3 and AR4 projections. The sea level rise rate specified in this study is 3.2 mm/year, and is about 60% greater than the rate projected in the IPCC AR3 and AR4. The authors also clearly state that the increased rate in sea level rise is not due to multi-decadal internal variability in the climate system, nor do other non-climatic components like groundwater extraction or reservoir water storage have an impact on data comparisons.
Stefan Rahmstorf, lead author of the study, stated: “This study shows once again that the IPCC is far from alarmist, but in fact has under-estimated the problem of climate change. That applies not just for sea-level rise, but also to extreme events and the Arctic sea-ice loss.”
Because climate projections should be a significant part of decision-making processes relating to climate change, it is essential that we know how past projections compare to accumulating observational data.
Read the Journal article: Comparing Climate Projections to Observations Up to 2011