Intergovernmental Panel on Climate Change Fourth Assessment and Beyond

(from AMSA Report 2009)

The Intergovernmental Panel on Climate Change (IPCC) was established in 1988 by the World Meteorological Organization of the United Nations Environment Programme. IPCC is an intergovernmental body that provides scientific and technical information to policy makers.

The 2007 IPCC 4th Assessment report indicated the lack of comprehensive sea ice data prior to the satellite era. However, observed data analyses have been able to confirm a sustained decline in Arctic sea ice since the early 1970s, notably during the summer melt season. The report also comments that the accuracy of satellite-derived ice concentration is usually 5 percent or better; errors of up to 10-20 percent can occur during the melt season as the passive microwave sensors measure the thin surface layers of melt water on the sea ice surface.

Of critical importance to future navigation, the assessment also summarizes the information on the remarkable decrease in multi-year ice throughout the Arctic Ocean. The possibility of an ice-free Arctic Ocean, even for a brief period, was advanced as an intriguing outcome of the ACIA. Recent analyses of GCM sea ice simulations using models from the IPCC AR4 (applying global warming scenarios) show near-complete loss of Arctic sea ice in September for 2040 to beyond 2100. However, additional research also indicates abrupt reductions in sea ice coverage during the 21st century are a common feature in many of the GCM simulations.

Whether these periods of accelerated summer sea ice retreat might provide windows of opportunity for improved marine navigation is unknown. However, these research results and recent model inter comparisons show the many uncertainties that remain in simulating the future ice cover of the Arctic Ocean. Further research on the performance of the IPCC AR4 models (Map 2.4) reveals that none of the GCMs have negative trends for sea ice as large as the observed sea ice coverage trend for the period 1953- 2006 (7.8 percent per decade reduction). The observed trend is three times larger than the multi-model mean of a 2.5 percent per decade loss. This is an extraordinary development that also means the current summer sea ice minima are as much as 30 years ahead of the mean of the model simulations.

Map 2.4 Hadley Centre Arctic Sea Ice Simulations, 2050 

Source: AMSA

With continued greenhouse gas emissions, it is highly plausible that the Arctic Ocean could become completely ice-free for a short summer period much earlier than 2040. Just as important to ship navigation, these simulations indicate large areas of the coastal Arctic seas to be ice-free for longer periods in the spring and autumn months. Arctic marine access continues to increase in nearly all the scenarios posed by the ACIA and the more recent IPCC assessments.

Arctic Council, 2009, Arctic Marine Shipping Assessment Report, Arctic Council.©