Understanding multi-decadal global warming rate changes

Understanding multi-decadal global warming rate changes
The surface temperature changes in multiple oceans determine the global warming rate changes. Credit: Gang Huang

Despite persistently increasing greenhouse gas emissions throughout the 20th and early 21st centuries, the globally averaged surface temperature has shown distinct multi-decadal fluctuations since 1900, including two weak global warming slowdowns in the mid-20th century and early 21st century and two strong global warming accelerations in the early and late 20th century. The multi-decadal global warming rate changes are primarily attributed to multiple ocean surface temperature changes, according to research by Institute of Atmospheric Physics and Australian Bureau of Meteorology?and It is the net impact of multiple ocean surface temperature changes, rather than a single ocean basin change, that plays a main driver for the multi-decadal global warming accelerations and slowdowns. Understanding and quantifying the respective role of individual ocean basin in the multi-decadal global warming accelerations and slowdowns, under the forcing of the sustained increase in atmospheric greenhouse gas concentrations, could help achieve a more accurate estimate of the future global warming rate to better meet the global warming target of the Paris Accords—no more than 1.5ºC above pre-industrial levels by 2100.

The new finding of the importance of multiple changes to the multi-decadal accelerations and slowdowns is supported by a set of computer modeling experiments, in which observed sea surface temperature changes are specified in individual ocean basins, separately. The results are published in Nature Climate Change.

"Our results identify multiple ocean surface temperature change as a major driver for global mean surface temperature changes on multi-decadal timescales. The paramount importance of multiple ocean basins in determining the global warming rates provides a new insight to improving global and regional climate projections," says corresponding author Gang Huang from Institute of Atmospheric Physics, Chinese Academy of Sciences (CAS).

"The results elucidate the relative contributions of individual ocean surface temperature changes to the multi-decadal global warming rate changes, and could help improve our understanding of global warming fluctuations under steadily increased emissions of atmospheric greenhouse gases," says Jing-Jia Luo, the corresponding author of the study and climate scientist at the Bureau of Meteorology in Australia. "It reveals the fact that we need to explore climate change in a more global perspective. This could stimulate an integrated strategy and coordinated effort toward understanding the causes of regional ocean changes."

"Our study provides a novel perspective for understanding and projecting individual ocean basin's impacts on global warming," explains co-author Dr. Shuai-Lei Yao from CAS Institute of Atmospheric Physics. "While the tropical Pacific was generally regarded as a key contributor to the multi-decadal global warming rate changes, other basins, including the Indian Ocean, the Atlantic and the Southern Ocean, also exert important effects. "

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More information: Shuai-Lei Yao et al, Distinct global warming rates tied to multiple ocean surface temperature changes, Nature Climate Change (2017). DOI: 10.1038/nclimate3304
Journal information: Nature Climate Change

Citation: Understanding multi-decadal global warming rate changes (2017, June 14) retrieved 16 September 2019 from https://phys.org/news/2017-06-multi-decadal-global.html
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Jun 15, 2017
It is scarcely a surprise to find that our present global warming is proceeding at different rates in different places and that in fact this phenomenon was present over a longer period of time than more popular news of it would suggest. So what is needed is some better organized data to separately cover the temperature changes over the past century or so for different parts of the arctic and ant-arctic ice caps, oceans and land masses.

Jun 15, 2017
As usual the author of this article is a member of the church of climatology, adding material not associated with the paper. Read the abstract and it reveals the subject is temperature oscillation and effect. So natural oscillation must be labeled as climate change. Note the authors name is absent.

Jun 16, 2017
Half a millennium of human observation -- solar activity paramount.
Long-term Variations in Solar Activity
and their Apparent Effect on the Earth's Climate
K.Lassen, 1998.
Danish Meteorological Institute.

The varying length of the 11-year cycle has been found to be strongly correlated with longterm variations of the northern hemisphere land surface air temperature since the beginning of systematic temperature variations from a global network, i. e. during the past 130 years. Although direct temperature observations before this interval are scarce, it has been possible to extend the correlation back to the 16th century due to the existence of a series of proxy temperature data published by Groveman and Landsberg in 1979. Reliable sunspot data do not exist before 1750, but we have been able to derive epochs of minimum sunspot activity from auroral observations back to 1500 and combine them with the direct observations to a homogeneous series...................

Jun 19, 2017
Very interesting article but ... in 2009, with two co-authors, I wrote a paper showing that the ENSO could account for the pattern in Lower Tropospheric Temperatures with a delay of about 7 months between an ENSO change and a corresponding change in LTT. Climategate emails show our critics discussing a criticism of our paper one of them wrote (and about six more put their names to), especially the part about which reviewers they might suggest to the journal. One of the suggested reviewers worked at the Bureau of Meteorology. It seems like the BoM might finally be admitting that our paper was correct.
(Before anyone says it, the Comment on our paper was published but not our reply, which the journal refused to publish, quite possibly because we pointed out factual and other errors in the Comment that peer-review of the Comment had failed to identify.) - John McLean

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