The ten hottest years on record globally all have occurred since 1998. Graphic: Climate Central

By Andrea Thompson
14 July 2017

(Climate Central) – When 2015 blew the record for hottest year out of the water, it made headlines around the world. But a heat record that was so remarkable only two years ago will be just another year by 2040 at the latest, and possibly as early as 2020, regardless of whether the greenhouse gas emissions warming the planet are curtailed.

That is the conclusion of a new study that uses climate models to project when today’s climate extremes will become commonplace — or the “new normal” as they are often called in both media reports and scientific analyses.

Just how soon that record heat will become the norm surprised even its researchers, but the information could be useful to officials around the world trying to plan for the changes global warming will bring to their cities and countries. It will help show when notable heat waves, downpours, or other extremes may become run-of-the-mill, and would allow planners to develop the infrastructure and policies to withstand those extremes.

“At the moment, it doesn’t seem like such a big deal when we have record-hot summers or years,” study leader Sophie Lewis, a climate researcher at Australian National University, said in an email. “But this study really shows the nasty side of our current records becoming more frequent in the near future.” [more]

Today’s Extreme Heat May Become Norm Within a Decade


ABSTRACT: The term “new normal” has been used in scientific literature and public commentary to contextualize contemporary climate events as an indicator of a changing climate due to enhanced greenhouse warming. A new normal has been used broadly but tends to be descriptive and ambiguously defined. Here we review previous studies conceptualizing this idea of a new climatological normal and argue that this term should be used cautiously and with explicit definition in order to avoid confusion. We provide a formal definition of a new climate normal relative to present based around record-breaking contemporary events and explore the timing of when such extremes become statistically normal in the future model simulations. Applying this method to the record-breaking global-average 2015 temperatures as a reference event and a suite of model climate models, we determine that 2015 global annual-average temperatures will be the new normal by 2040 in all emissions scenarios. At the regional level, a new normal can be delayed through aggressive greenhouse gas emissions reductions. Using this specific case study to investigate a climatological new normal, our approach demonstrates the greater value of the concept of a climatological new normal for understanding and communicating climate change when the term is explicitly defined. This approach moves us one step closer to understanding how current extremes will change in the future in a warming world.

Defining a New Normal for Extremes in a Warming World

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