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| 3. Instrumental Temperature Record, and Ocean Acidification |
| Average Global Temperature 1880-2009 | Dissolved CO2 and Ocean Acidity (pH) |
|---|---|
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| This figure shows the average global temperature during the period 1880-2009, compiled from various data sources by NASA's Goddard Institute for Space Studies. Zero in this figure is the average temperature for the period 1961-1990. The red curve is a 5-year average that brings out the trend underlying the year-to-year variability. References for the data sources and analysis methods behind this figure are given at Global Warming Art.
All measurements have uncertainty, which is sometimes called "error", but I like "uncertainty" better because error sounds like it was a mistake and we even know how big the mistake is. This isn't the idea, because known biases in the measurements would be accounted for. Measurements are imperfect for a variety of reasons, ranging from the accuracy of the instrumentation to sampling uncertainty from incomplete data coverage. "Uncertainty" is an estimate of the expected accuracy of measurements considering the imperfections. The uncertainty analysis for this dataset gives an expected accuracy of ±0.05°C at the 95% confidence level for measurements since 1950, increasing for older measurements to ±0.15°C in 1890. Considering these uncertainties, the estimated average global temperature change from 1901 to 2000 is 0.57±0.17°C, where ±0.17°C is the uncertainty in the estimate at the 95% confidence level. Figure created by Robert A. Rohde from published data for Global Warming Art. |
This figure shows the correlation between rising levels of carbon dioxide (CO2) in the atmosphere at Mauna Loa (red) with rising levels of CO2 dissolved in the ocean at nearby Station Aloha (blue), and the consequent increase in acidity of the ocean seen as a decrease in ocean pH (green). Global warming from CO2 deals a double blow to the oceans because not only does the ocean warm by absorbing part of the atmospheric temperature increase, it also absorbs about one-third of the increase in CO2, which reacts with water to produce carbonic acid. So, the oceans help to decrease atmospheric CO2 and slow global warming, but with major negative consequences for the chemistry and biology of the oceans.
Many creatures in the ocean require a fairly narrow range of temperature and/or pH to survive. A warming ocean causes creatures that can move, like jellyfish, to move northward to cooler waters, and those that can't move, like coral, to die of heat stress. Acidification interferes with the formation of shells made of calcium carbonate, because decreasing pH means decreasing availability of carbonate ions. Some of those shelled creatures are microscopic and are at the base of the food chain, so their demise affects all ocean life as well as we humans who depend on it. The acidity of the oceans has already increased by 30% (0.1 pH units) from pre-industrial times, and it will continue to increase as long as humans continue burning fossil fuels and adding more CO2 to the atmosphere. For more information about ocean acidification, see this report from the Center for Climate and Energy Solutions. Source: Ocean Acidification by R.A. Feely, page 60 in Levinson, D.H. and J.H. Lawrimore, 2008: State of the Climate in 2007. Bull. Amer. Meteor. Soc., 89, S1-S179.
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