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Record Warming 2014
Global temperatures January-October
According to the US National Oceanic and Atmospheric Administration (NOAA) the first ten months of 2014 (January-October) were the warmest such period since record keeping began in 1880. Global land and ocean average surface temperature reached 0.68 °C above the 20th century average of 14.1°C. Making 2014 on track to become the warmest year on record. Record warmth for the year so far has been particularly notable across much of northern and western Europe, parts of far east Russia, and large areas of the northeastern and western equatorial Pacific Ocean.
Source: NOAA, 2014
Sweden was warmer than average during October, with the southern half of the country experiencing temperatures 2-4°C above their October averages (SMHI). On October 28, the daily temperature in Stockholm was 14.2°C, the highest daily average observed so late in the year since records began in 1756.
Northern Hemisphere is warming faster
Looking at historical records of Land and Ocean surface mean temperature anomalies we can see that the northern hemisphere is warming much faster, with some of the most rapid warming rates on Earth located in the Arctic, where sea and land ice is shrinking and thinning.
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| Source: NOAA, 2014 |
Changes in albedo (i.e. reflectivity) difference between the Arctic and Antarctic and global ocean currents contribute to the Northern Hemisphere’s rapid warming, according to researchers from Potsdam Institute for Climate Impact (Feulner et al. 2013). Currents transport heat away from southern waters and into the North Atlantic and North Pacific, helping to warm nearby land areas in the north even more. For example, the Gulf Stream, which carries heat from the tropics far into the North Atlantic, along the Scandinavian west coast (see map).
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| Source: Tellus |
Melting Arctic = More Extreme Weather?
Temperatures in the Arctic have risen twice as fast as the rest of the world, a phenomenon known as Arctic amplification (Cohen et al. 2014). Scientists have linked the rapid rise in Arctic temperatures over the past two decades to weather extremes in the Northern Hemisphere such as heatwaves in the US and flooding in Europe (Coumou et al. 2014, Francis 2014). Rapid warming in the Arctic can have triggered changes to global wind patterns, which have brought extreme weather to lower latitudes. Extreme weather events have almost doubled over the last two decades. Now researchers think that this can be linked with unusual weather patterns in the upper atmosphere, influenced by warmer Arctic temperatures. They believe that the loss of sea ice in the Arctic may be contributing to the appearance of wide north-south swings in the high-altitude winds flowing globally west to east around the polar region, causing them to “get stuck” and amplified in a quasi-stationary pattern known as a “standing wave”. When interviewed by the Independent one of the researchers, Stefan Rahmstorf, said “Evidence for actual changes in planetary wave activity was so far not clear. But by knowing what patterns to look for, we have now found strong evidence for an increase in these resonance events” (Professor of Physics and co-chair of Earth System Analysis at Potsdam University). The possibility of a link between Arctic change and mid-latitude weather has spurred research activities that reveal three potential dynamical pathways: changes in storm tracks, the jet stream, and planetary waves and their associated energy propagation (Cohen et al. 2014).Changes in precipitation
A study from Berkeley has projected that if emissions remain on their present upward trajectory, the average temperature difference between the two hemispheres could be about 1.6°C. This would be sufficient to alter tropical rainfall patterns, which could affect everything from rice cultivation in India to the health of the Amazonas Rainforest (Friedman et al. 2013). According to the authors, tropical rain bands that form near the equator where trade winds collide to build up thunderstorms may shift northward, drying out parts of the Southern Hemisphere, while causing more precipitation in the North.
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