Natural variations help resolve a climate puzzle, say researchers

Credit: concernusa.org

Well, knock me down with a feather. Real world data can expose flaws in ‘greenhouse gas’ infected climate models, which are unable to model El Niño and La Niña events, and mostly predict much more warming than actually occurs.
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New research shows that naturally occurring climate variations help to explain a long-standing difference between climate models and satellite observations of global warming, says Phys.org.

Satellite measurements of global-scale changes in atmospheric temperature began in late 1978 and continue to the present.

Relative to most model simulations, satellite data has consistently shown less warming of Earth’s lower atmosphere.

This has led some researchers to conclude that climate models are too sensitive to greenhouse gas emissions, and thus are not useful for making future climate change projections.

Instead, the model-versus-satellite difference is largely driven by natural variations in the Earth’s climate.

“Natural climate variability has likely reduced the observed warming during the satellite-era” said Stephen Po-Chedley, a Lawrence Livermore National Laboratory (LLNL) climate scientist and lead author of a paper appearing in the Proceedings of the National Academy of Sciences.

The main driver of natural year-to-year variations in global climate is the El Niño-Southern Oscillation (ENSO). Every few years, ENSO produces an El Niño event, which results in widespread warming of the atmosphere and ocean lasting several months.

The cold phase of ENSO is La Niña, which cools the atmosphere and gives rise to a distinct pattern of cooler-than-usual sea surface temperatures in the central and eastern tropical Pacific, with warmer waters to the north and south.

Many climate models produce ENSO variations, but the timing of these events is not specified in model simulations. “While models are intended to represent the average climate, its changes and realistic natural variations, they can only simulate the exact timing of natural climate events by chance,” said Po-Chedley.

Some decades favor El Niño or La Niña events. Clustering of El Niño and La Niña events can create decadal oscillations that influence the rate of atmospheric warming.

Simulations with coupled models of the atmospheric and ocean circulation produce such decadal oscillations, but their phasing will not necessarily match the real world during the satellite era.

Qiang Fu, professor at the University of Washington and an author of the study, notes that, “while it is well-known that natural variability can produce decade-long periods of subdued warming, this study demonstrates that it also can play an important role over the relatively long 40-year timescales that are relevant to satellite records.”

Climate models typically simulate substantially more warming than satellite data in the tropical troposphere (the lowest region of the atmosphere, extending from the Earth’s surface to a height of about 11 miles).

Continued here.

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March 23, 2021 at 07:57AM

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