Climate Change Research Spotlight

Was the Recent Slowdown in Surface Warming Predictable?

The temporary deceleration in warming across the Northern Hemisphere earlier this century could not have been foreseen by statistical forecasting methods, a new study concludes.

Source: Geophysical Research Letters

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From the early 2000s to the early 2010s, there was a temporary slowdown in the large-scale warming of Earth’s surface. Recent studies have ascribed this slowing to both internal sources of climatic variability—such as cool La Niña conditions and stronger trade winds in the Pacific—and external influences, including the cooling effects of volcanic and human-made particulates in the atmosphere.

Several studies have suggested that climate models could have predicted this slowdown and the subsequent recovery several years ahead of time—implying that the models can accurately account for mechanisms that regulate decadal and interdecadal variability in the planet’s temperature. To test this hypothesis, Mann et al. combined estimates of the Northern Hemisphere’s internal climate variability with hindcasting, a statistical method that uses data from past events to compare modeling projections with the already observed outcomes.

The team’s analyses indicate that statistical methods could not have forecast the recent deceleration in surface warming because they can’t accurately predict the internal variability in the North Pacific Ocean, which played a crucial role in the slowdown. In contrast, a multidecadal signal in the North Atlantic does appear to have been predictable. According to their results, however, its much smaller signal means it will have little influence on Northern Hemisphere temperatures over the next 1 to 2 decades.

This minor signal in the North Atlantic is consistent with previous studies that have identified a regional 50- to 70-year oscillation, which played a more important role in controlling Northern Hemisphere temperatures in the middle of the 20th century than it has so far this century. Should this oscillation reassume a dominant role in the future, argue the researchers, it will likely increase the predictability of large-scale changes in Earth’s surface temperatures. (Geophysical Research Letters, doi:10.1002/2016GL068159, 2016)

—Terri Cook, Freelance Writer

Citation: Cook, T. (2016), Was the recent slowdown in surface warming predictable?, Eos, 97, doi:10.1029/2016EO051477. Published on 11 May 2016.

© 2016. The authors. CC BY-NC-ND 3.0
  • STeamPlayer

    This is an issue where the denialists got ahead. For years they’ve been talking about the data indicating global temperatures stopped rising since around 1997, and in response climate scientists have dodged that evidence, mostly with statistical arguments. Essentially these climate scientists went into denial mode.

    Now that the evidence for the warming hiatus has become undeniable, the climate scientists have renamed it a “temporary deceleration” and are finally starting to think about it seriously, and are learning more about why it happened. The lesson? The science community must always remain true to its principles of objectivity, despite the onslaught of denialist propaganda. In other words, just because denialists say something, that doesn’t mean it’s untrue.

  • Tebsonini

    The short term isn’t important. It takes decades for CO2 levels to have their full effect on climate. In the long term global temperature and CO2 levels have to trend together. That is because temperature and CO2 trends are cointegrated to an extreme extent. In statistics, cointegration means that when two variables are cointegrated, any departure in their trends can only be short term. This simple statistical technique is more important than the complicated modeling done by climate scientists..

  • NO2BHO

    The statistical methods used by Mann et al could not have predicted the cooling, the same way they’ve been horribly wrong all along!! What gives any of the Flat-Earther AGW supporters any credibility regarding forecasts of temperature readings??? Nothing!