The oceans are warming faster than we thought, and scientists suggest we brace for impact
Source: Washington Post
The oceans are warming faster than we thought, and scientists suggest we brace for impact
By Angela Fritz January 11 at 5:25 PM
The oceans are warming faster than climate reports have suggested, according to a new synthesis of temperature observations published this week. The most recent report from the United Nations Intergovernmental Panel on Climate Change made what turned out to be a very conservative estimate of rise in ocean temperature, and scientists are advising us to adjust our expectations.
“The numbers are coming in 40 to 50 percent [warmer] than the last IPCC report,” said Kevin Trenberth, a climate scientist at the National Center for Atmospheric Research and an author on the report, published in Science Magazine on Thursday.
Furthermore, Trenberth said, “2018 will be the warmest year on record in the oceans" as 2017 was and 2016 before that.
Oceans cover 70 percent of the globe and absorb 93 percent of the planet’s extra heat from climate change. They are responsible for spawning disasters like hurricanes Florence and Maria and generating torrential rainfall via meteorological processes with names like “atmospheric river” and “Pineapple Express.”
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Read more: https://www.washingtonpost.com/weather/2019/01/11/oceans-are-warming-faster-than-we-thought-scientists-suggest-we-brace-impact/
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Source: Science Magazine
How fast are the oceans warming?
Lijing Cheng, John Abraham, Zeke Hausfather, Kevin E. Trenberth
Science 11 Jan 2019:
Vol. 363, Issue 6423, pp. 128-129
DOI: 10.1126/science.aav7619
Climate change from human activities mainly results from the energy imbalance in Earth's climate system caused by rising concentrations of heat-trapping gases. About 93% of the energy imbalance accumulates in the ocean as increased ocean heat content (OHC). The ocean record of this imbalance is much less affected by internal variability and is thus better suited for detecting and attributing human influences (1) than more commonly used surface temperature records. Recent observation-based estimates show rapid warming of Earth's oceans over the past few decades (see the figure) (1, 2). This warming has contributed to increases in rainfall intensity, rising sea levels, the destruction of coral reefs, declining ocean oxygen levels, and declines in ice sheets; glaciers; and ice caps in the polar regions (3, 4). Recent estimates of observed warming resemble those seen in models, indicating that models reliably project changes in OHC.
The Intergovernmental Panel on Climate Change's Fifth Assessment Report (AR5), published in 2013 (4), featured five different time series of historical global OHC for the upper 700 m of the ocean. These time series are based on different choices for data processing (see the supplementary materials). Interpretation of the results is complicated by the fact that there are large differences among the series. Furthermore, the OHC changes that they showed were smaller than those projected by most climate models in the Coupled Model Intercomparison Project 5 (CMIP5) (5) over the period from 1971 to 2010 (see the figure).
Since then, the research community has made substantial progress in improving long-term OHC records and has identified several sources of uncertainty in prior measurements and analyses (2, 6–8). In AR5, all OHC time series were corrected for biases in expendable bathythermograph (XBT) data that had not been accounted for in the previous report (AR4). But these correction methods relied on very different assumptions of the error sources and led to substantial differences among correction schemes. Since AR5, the main factors influencing the errors have been identified (2), helping to better account for systematic errors in XBT data and their analysis.
Several studies have attempted to improve the methods used to account for spatial and temporal gaps in ocean temperature measurements. Many traditional gap-filling strategies introduced a conservative bias toward low-magnitude changes (9). To reduce this bias, Domingues et al. (10) used satellite altimeter observations to complement the sparseness of in situ ocean observations and update their global OHC time series since 1970 for the upper 700 m. Cheng et al. (2) proposed a new gap-filling method that used multimodel simulations to provide an improved prior estimate and error covariance. This method allowed propagation of information from data-rich regions to the data gaps (data are available for the upper 2000 m since 1940). Ishii et al. (6) completed a major revision of their estimate in 2017 to account for the previous underestimation and also extended the analysis down to 2000 m and back to 1955. Resplandy et al. (11) used ocean warming outgassing of O2 and CO2, which can be isolated from the direct effects of anthropogenic emissions and CO2 sinks, to independently estimate changes in OHC over time after 1991.
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Read more: http://science.sciencemag.org/content/363/6423/128
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