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Climate extremes are here to stay: Expect more heat waves and cold snaps

July 30, 2014
Northeastern University
Researchers show how they've used advanced computational data science tools to demonstrate that despite global warming, we may still experience severe cold snaps due to increasing variability in temperature extremes.

Cold snowy road. Even as overall tem­per­a­tures rise, we may still con­tinue to expe­ri­ence extreme cold snaps.
Credit: © pergo70 / Fotolia

By now, most sci­en­tists -- 97 per­cent of them, to be exact -- agree that the tem­per­a­ture of the planet is rising and that the increase is due to human activ­i­ties such as fossil fuel use and defor­esta­tion. But until recently, the jury was still out regarding the vari­ability sur­rounding that increase -- for example, how much dif­fer­ence there will be between the hottest hot days from one year to the next, as well as with each year's coldest cold days.

Some studies sug­gested an increase in vari­ability, others a decrease. The problem with these results, said Evan Kodra, PhD'14, is that none of them took a sys­tem­atic approach to gleaning that answer. Each was exam­ining some other phenomenon -- such as whether a par­tic­ular region would expe­ri­ence overall warming -- and the vari­ability data was a sec­ondary, but inter­esting, finding.

That's why Kodra and his adviser Auroop Gan­guly, a cli­mate change expert and asso­ciate pro­fessor in Northeastern's Depart­ment of Civil and Envi­ron­mental Engi­neering, decided to take a dif­ferent approach in their paper recently pub­lished online in the journal Sci­en­tific Reports, pub­lished by Nature. Their work was per­formed in Northeastern's Sus­tain­ability and Data Sci­ences Lab­o­ra­tory run by Ganguly.

What they found may sur­prise some: While global tem­per­a­ture is indeed increasing, so too is the vari­ability in tem­per­a­ture extremes. For instance, while each year's average hottest and coldest tem­per­a­tures will likely rise, those aver­ages will also tend to fall within a wider range of poten­tial high and low tem­perate extremes than are cur­rently being observed.

This means that even as overall tem­per­a­tures rise, we may still con­tinue to expe­ri­ence extreme cold snaps, said Kodra, who earned the Col­lege of Engineering's out­standing grad­uate research award in 2014 and is now leading data ana­lytics efforts at Energy Points, an inno­v­a­tive Boston area startup.

That is an impor­tant point in the ongoing effort to accu­rately inform the public about cli­mate change. "Just because you have a year that's colder than the usual over the last decade isn't a rejec­tion of the global warming hypoth­esis," Kodra explained.

The new results pro­vide impor­tant sci­en­tific as well as soci­etal impli­ca­tions, Gan­guly noted. For one thing, knowing that models project a wider range of extreme tem­per­a­ture behavior will allow sec­tors like agri­cul­ture, public health, and insur­ance plan­ning to better pre­pare for the future. For example, Kodra said, "an agri­cul­ture insur­ance com­pany wants to know next year what is the coldest snap we could see and hedge against that. So, if the range gets wider they have a broader array of poli­cies to consider."

With funding from a $10-​​million multi-​​university Expe­di­tions in Com­puting grant on under­standing cli­mate change, the duo used com­pu­ta­tional tools from Big Data sci­ence to sys­tem­at­i­cally examine this aspect of cli­mate change for the first time. This study did just that, bringing together a unique com­bi­na­tion of com­pu­ta­tional data sci­ence tools tai­lored for extracting nuanced insights about cli­mate extremes.

The research also opens new areas of interest for future work, both in cli­mate and data sci­ence. It sug­gests that the nat­ural processes that drive weather anom­alies today could con­tinue to do so in a warming future. For instance, the team spec­u­lates that ice melt in hotter years may cause colder sub­se­quent win­ters, but these hypotheses can only be con­firmed in physics-​​based studies.

The study used sim­u­la­tions from the most recent cli­mate models devel­oped by groups around the world for the Inter­gov­ern­mental Panel on Cli­mate Change and "reanalysis data sets," which are gen­er­ated by blending the best avail­able weather obser­va­tions with numer­ical weather models. The team com­bined a suite of methods in a rel­a­tively new way to char­ac­terize extremes and explain how their vari­ability is influ­enced by things like the sea­sons, geo­graph­ical region, and the land-​​sea inter­face. The analysis of mul­tiple cli­mate model runs and reanalysis data sets was nec­es­sary to account for uncer­tain­ties in the physics and model imperfections.

Story Source:

Materials provided by Northeastern University. Original written by Angela Herring. Note: Content may be edited for style and length.

Journal Reference:

  1. Evan Kodra, Auroop R. Ganguly. Asymmetry of projected increases in extreme temperature distributions. Scientific Reports, 2014; 4 DOI: 10.1038/srep05884

Cite This Page:

Northeastern University. "Climate extremes are here to stay: Expect more heat waves and cold snaps." ScienceDaily. ScienceDaily, 30 July 2014. <>.
Northeastern University. (2014, July 30). Climate extremes are here to stay: Expect more heat waves and cold snaps. ScienceDaily. Retrieved April 27, 2017 from
Northeastern University. "Climate extremes are here to stay: Expect more heat waves and cold snaps." ScienceDaily. (accessed April 27, 2017).