How much time is there left to act?

Global temperatures are rising fast, as illustrated on the interactive graph below, showing NASA data for the years 1980 to 2011.

In the Arctic, temperatures are rising even faster. To compare the rise in the Arctic with the global one, it makes sense to look at anomalies.

The interactive chart below shows anomalies at higher latitudes, i.e. 64 degrees North and higher, up to the North Pole. For both the years 2010 and 2011, NASA recorded mean anomalies of over 2°C at all higher latitudes (64N to 90N), while specific latitudes (79N and 81N) reached anomalies of over 3°C in 2010.

For specific months, anomalies can be very high. In November 2010, anomalies of 12.5°C were recorded at latitude 71N, longitude -79 (Baffin Island, Canada). At specific moments in time and at specific locations, anomalies can be even more striking. As an example, on January 6, 2011, temperature in Coral Harbour, located at the northwest corner of Hudson Bay in the province of Nunavut, Canada, was 30°C (54°F) above average.

    

The image on the left has a trend line added showing how temperature anomalies are projected to continue, based on historic data from 1964 to 2011.

Underneath on the left, an interactive chart showing global land temperature anomalies.

Further down on the left, an image combining these images into one.

The danger of such huge temperature rises in the Arctic is that they will trigger releases of methane from hydrates and free gas in sediments under the sea. What will be the impact of abrupt release of, say, 1Gt of methane? Let's compare this with the global carbon dioxide emissions from fossil-fuel burning, cement manufacture, and gas flaring, as illustrated by the interactive image below, based on CDIAC data 1751-2010 (incl).

Methane has an initial global warming potential (GWP) of over 100 times that of carbon dioxide. Abrupt release of 1Gt of methane would thus have an immediate additional impact equivalent to over 100Gt of carbon dioxide, as illustrated by the image below.

Abrupt release of 1Gt of methane is pictured above as a one-off pulse. Its impact, however, will persist over many years, not only due to the direct effect of methane, but also due to indirect effects.

Some may argue that methane has an average lifetime of only about ten years, which would make its warming impact decline rapidly over the years, in the end merely only persisting as carbon dioxide, as pictured below.

However, crucially important is methane's local warming potential (LWP), which includes the indirect effect of triggering further releases. In case of a large abrupt release, methane's lifetime will be extended, due to hydroxyl depletion. The methane can be expected to persist locally for decades, at its highest LWP, since there's very little hydroxyl in the atmosphere above the Arctic in the first place, so very little methane will get oxidized there. The impact of such an abrupt release will be felt most in the Arctic, where the release took place. Since it will take time for methane to spread away from the Arctic, much of the entire release will remain concentrated above the Arctic.

The additional warming that this will cause in the Arctic will make the sea ice decline even more dramatically than is already the case now. The combined LWP of sea ice loss and methane is huge. This is bound to trigger further releases of methane in the Arctic, and their joint impact will accumulate, as illustrated in the image below.

Warming will first strike in the Arctic, but will soon spread, threatening to cause heatwaves and firestorms across North America and Siberia, which will add additional soot and carbon dioxide in the atmosphere globally, as forests, peat bogs and tundras at higher latitudes will burn, threatening to escalate in runaway global warming.

Editor's note: for an update, see the page at the Arctic-news blog How much time is there left to act?