Future Ocean & the Climate of the 21st Century. Daniela Schmidt, @Nature.

Dec 08, 2016, 07:14 AM

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Future Ocean & the Climate of the 21st Century. Daniela Schmidt, @Nature.

Prof. Daniela Schmidt Professor in Palaeobiology School of Earth Sciences Science Faculty Research Director Royal Society Wolfson Research Merit Scholar

“ NOISY WATERS The impacts of climate change on the oceans are usually depicted using graphs. Lines represent projections of long-term globally averaged quantities such as relentless rises in mean sea surface temperature or acidifica¬tion. But the real ocean is noisy. Its conditions simultaneously undergo fast and slow varia¬tions as well as local, regional and global ones. It is important to quantify the long-term average state of the ocean. Eventually, the influence of anthropogenic climate change will be larger than that of ongoing natural variability3. This transition is known as the emergence. But we are not there yet. The present oceanic signature of anthropogenic climate change is still comparable to, and thus difficult to disentangle from, natural and regional climate variability such as the El Niño Southern Oscillation, cycles in winds and sea surface temperatures over the tropi¬cal east Pacific Ocean. Emergence will happen at different times in different places. For example, the tropics are already recording extreme temperatures, whereas the emergence is several decades away at mid-latitudes4

Natural climate variability can offset or amplify climate change trends temporarily (see ‘Reading the waves’). For example, an apparent5 slowing or ‘hiatus’ in global aver¬age temperature rise between 1998 and 2012 led some critics to downplay anthropogenic climate change. Natural variability also reflects more extreme conditions, such as latest strong El Niño warming event. As anthropogenic climate change increases, periods of extreme conditions6 are expected to become more frequent, severe and lengthy. These will have adverse effects on marine ecosystems7. For example, in 2011 the west coast of Australia encoun¬tered sea surface temperatures that were 2–4 °C warmer than average for 10 weeks. Its kelp forest, usually 800 kilometres long, shrank by 43%7. These fluctuations are confusing for marine-resource managers, policymakers and the public. They make decisions about how best to adapt to climate change difficult, and short term forecasts unreliable. …. “