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Black contours show the mass flux streamfunction, with dashed negative contours indicating clockwise motion and solid positive contours indicating counterclockwise motion. Colors indicate horizontal eddy momentum flux divergence , with the overbar denoting a temporal and zonal mean and primes denoting deviations therefrom i.
Flow statistics are computed from reanalysis data for the years — provided by the European Centre for Medium-Range Weather Forecasts Kallberg et al. Mass flux streamfunction black contours and horizontal eddy momentum flux divergence color contours. Plotting conventions and contour intervals are as in Fig.
Differences between the Northern and Southern Hemisphere are indicative of sampling variability. Mean zonal wind black contours and potential temperature gray contours. Dashed black contours indicate easterlies and solid black contours indicate westerlies. Strength of the Hadley circulation in simulations with solid with circles and without dashed—dotted with squares ocean heat transport. Filled symbols identify the reference simulations in this and subsequent figures.
Bulk Rossby number in the simulations with solid with circles and without dashed—dotted with squares ocean heat transport. Eddy component of the mass flux streamfunction in the simulations with solid with circles and without dashed—dotted with squares ocean heat transport.
Mean available potential energy dashed—dotted with squares and eddy kinetic energy solid with circles integrated over baroclinic zones, and globally integrated positively signed eddy momentum flux divergence dashed with diamonds. Quantities are averaged over both hemispheres. Extent of the Hadley circulation vs global-mean surface temperature. Based on quantities averaged over both hemispheres. Simulations a with and b without ocean heat transport. Vertically integrated heat fluxes evaluated at the center of the Hadley cells latitude of the streamfunction extremum.
Total ocean—atmosphere heat flux red solid with circles and its components: mean component black solid with circles and eddy component green dashed—dotted with diamonds of the moist static energy flux; ocean heat flux orange dashed with squares.
The fluxes are averaged over both hemispheres. It is unclear how the width and strength of the Hadley circulation are controlled and how they respond to climate changes. Simulations of global warming scenarios with comprehensive climate models suggest the Hadley circulation may widen and weaken as the climate warms.
But these changes are not quantitatively consistent among models, and how they come about is not understood. Here, a wide range of climates is simulated with an idealized moist general circulation model GCM coupled to a simple representation of ocean heat transport, in order to place past and possible future changes in the Hadley circulation into a broader context and to investigate the mechanisms responsible for them.
The difference in trends between models and reanalyses poses a problem that goes far beyond whether the Hadley cell is going to weaken or strengthen; the inconsistency itself is a major concern for scientists.
Reanalyses are used to validate the reliability of climate models —if the two disagree, that means that either the models or reanalyses are flawed. To find the cause of this discrepancy, the scientists looked closely at the various processes that affect circulation, determining that latent heating is the cause of the inconsistency. To understand which data was correct—the models or the reanalyses—they had to compare the systems using a purely observational metric, untainted by any model or simulation.
In this case, precipitation served as an observational proxy for latent heating since it is equal to the net latent heating in the atmospheric column. This observational data revealed that the artifact, or flaw, is in the reanalyses—confirming that the model projections for the future climate are, in fact, correct.
Hence, any changes in the strength of the Hadley cell will result in a change in precipitation in that region. This is why it is important to determine if, as a consequence of anthropogenic emission, the Hadley cell will speed up or slow down in the coming decades.
But these findings resonate far beyond the study in question. Climate change is making droughts more likely to occur - and more severe when they do. Climate change is increasing the size, frequency, and intensity of wildfires. Earth Systems. Global warming is causing widespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere. What is Climate Signals? Climate Signals curates attribution science and provides resources in real time explaining how climate change worsens extreme weather and other impacts.
Climate change is increasing the risk of flooding due to a variety of reasons including rising sea levels and increasing extreme precipitation events. Rising air and ocean temperatures due to climate change are increasing hurricane precipitation, intensity, and the risk of coastal flooding.
Resource Hub. Real Time Data. Science Sources. What is climate attribution? Climate change attribution tells us how much of the credit or risk for a trend or event should go to human-caused climate change. Report: Fingerprints Everywhere Studies since the s show human-caused climate change directly influenced many recent trends and events. Attribution science database. An updating database of studies that find the fingerprint of human-caused climate change on observed trends and events.
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