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Daily RC Article 159

El Ni?o's Return and the Climate Change Debate: Impacts, Politics, and Future Scenarios

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Global warming occurs due to increased atmospheric greenhouse gas concentrations. An increase in atmospheric carbon dioxide (CO2) levels has resulted in the partial melting of the icecaps. Ice sheet formation was triggered when atmospheric CO2 fell below 750 ppmv, some 34 million years ago, during the Eocene-Oligocene transition.

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Scientists used boron isotope-II analysis of the carbonate shells of planktonic foraminifera (microorganisms) to understand the link between atmospheric CO2 levels and Antarctic ice sheet formation. The amount of boron isotope present in the carbonate shells increases as pH of the ocean surface water increases. Changes in pH of the ocean surface water in turn are governed by atmospheric CO2. pH of the ocean surface water increases (becomes alkaline) when atmospheric CO2 reduces. More the acidity of ocean water less will be the growth of carbonate shells and vice versa. Elevated levels of atmospheric CO2 seen today have made the ocean acidic. There is significant increase in the boron isotope in the period of global cooling. The decline in atmospheric CO2 may have contributed to global cooling and preconditioned the system for explosive ice sheet growth around 33.5 million years ago.

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This year’s El Niño might represent a turning point. The oscillation between El Niño and La Niña, El Niño’s cold-water cousin, is part of the reason for slower atmospheric warming. Sea surface temperatures in the Pacific rise during El Niño and ultimately heat up the atmosphere. The reverse happens during La Niña. The shifts between El Niño and La Niña offer an elegant explanation for at least some or perhaps most of the slowdown in atmospheric warming, after the historic El Niño of 1997 and early 1998. La Niña has often prevailed since then, cooling the atmosphere.

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The return of El Niño is likely to increase global temperatures. As El Niño returns heat from the oceans to the atmosphere, the ensuing spike in global surface temperatures could earn considerable news media attention, especially if they coincide with the extreme weather events typically brought by El Niño.

A strong El Niño causes a shift in a longer cycle known as the Pacific Decadal Oscillation (P.D.O.), which favors more frequent and intense El Niños during its “warm” or “positive” phase. If this fall’s El Nino kicks the P.D.O. into a positive phase, a result would be faster warming, at least doubling the rate of surface temperature increases.

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The accompanying wave of headlines might energize climate change activists and refocus attention on climate change heading into the presidential election. Those headlines could include landslides in Southern California, or widespread floods across the South. The timing could provide an uncomfortable backdrop for Republican presidential hopefuls who are skeptical of climate change. Democrats, eager to cast Republicans as anti-science or to appeal to voters in Miami, might be likelier to re-emphasize climate change if polls show an increase in the public’s belief in global warming, which will happen if global temperatures rise to record levels.

Mark McKinnon, a Republican strategist, thinks recurring catastrophic events will be necessary to soften the G.O.P."s position on climate change. Without Republican support, it will be hard for Congress to pass climate legislation.

The article discusses the relationship between global warming and various factors, including El Ni?o's impact on atmospheric warming. It touches on the connection between CO2 levels, ice sheet formation, and the oscillation between El Ni?o and La Ni?a. With the return of El Ni?o, there's a forecasted increase in global temperatures, potentially impacting climate change discussions and political views on the matter. There's also speculation about the role of these events in shaping political attitudes toward climate legislation.
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