Science - USA (2022-02-18)

( 6 , 8 – 11 ). These results suggest that any

short-lived cooling effect from disruptions

of the polar vortex is not sufficiently large

to cause long-term cooling trends over the

United States; instead, warming trends

are seen in observations and models.

Although we must investigate all pos-

sible consequences of climate change,

even those that may seem counterintui-

tive, context is important. Observations

and models strongly suggest that Arctic

change is reducing, not increasing, the

risk of winter cold extremes over the

United States. The mechanism proposed

by Cohen et al. may be relevant for year-

to-year variability, but the evidence does

not support a long-term increase in severe

winter weather.

Russell Blackport^1 *, John C. Fyfe^1 , James A. Screen^2

(^1) Canadian Centre for Climate Modelling and
Analysis, Environment and Climate Change
Canada, Victoria, BC, Canada.^2 College of
Engineering, Mathematics, and Physical Sciences,
University of Exeter, Exeter, UK.
*Corresponding author.
Email: [email protected]
REFERENCES AND NOTES

1. R. S. Vose, D. R. Easterling, K. E. Kunkel, A. N. LeGrande,
   M. F. Wehner, in “Climate science special report: Fourth
   National Climate Assessment, Volume I” (US Global
   Change Research Program, Washington, DC, 2017),
   pp. 185–206.
   2. G. J. van Oldenborgh et al., Environ. Res. Lett. 14 ,
   114004 (2019).
   3. G. J. van Oldenborgh, R. Haarsma, H. D. Vries, M. R. Allen,
   Bull. Am. Meteorol. Soc. 96 , 707 (2015).
   4. E. T. Smith, S. C. Sheridan, Geophys. Res. Lett. 47 ,
   e2020GL086983 (2020).
   5. A. Rhines, K. A. McKinnon, M. P. Tingley, P. Huybers,
   J. Climate. 30 , 1139 (2017).
   6. T. W. Collow, W. Wang, A. Kumar, J. Climate. 32 ,
   5021 (2019).
   7. R. Blackport, J. C. Fyfe, J. A. Screen, Nat. Geosci. 14 ,
   719 (2021).
   8. J. A. Screen, C. Deser, L. Sun, Bull. Am. Meteorol. Soc.
   96 , 1489 (2015).
   9. L. Sun, J. Perlwitz, M. Hoerling, Geophys. Res. Lett. 43 ,
   5345 (2016).
   10. T. Schneider, T. Bischoff, H. Płotka, J. Climate. 28 ,
   2312 (2015).
   11. S. Chripko et al., J. Climate. 34 , 5847 (2021).

10.1126/science.abn2414

Response

We agree with Blackport et al. that the

overall influence of global warming is to

decrease the occurrence of cold extremes.

However, global climate models consis-

tently predict winter temperatures that

are colder than those observed in the

Arctic and warmer than those observed in

Northern Hemisphere mid-latitudes ( 1 , 2 ).

Our Report was not meant to suggest that

cold extremes in the United States are

increasing in frequency overall, although a

SCIENCE science.org 18 FEBRUARY 2022 • VOL 375 ISSUE 6582 729

PHOTO: REUTERS/MIKE SEGAR

Editorial Expression

of Concern

On 22 August 2014, Science published the

Research Article “Chemically mediated

behavior of recruiting corals and fishes:

A tipping point that may limit reef recov-

ery” by D. L. Dixson et al. ( 1 ). Science has

been made aware of data manipulation

accusations pertaining to this paper. We

are publishing this Editorial Expression

of Concern to make readers aware of

these accusations while the lead author’s

current and postdoctoral institutions

investigate the claims. 

H. Holden Thorp

Editor-in-Chief

REFERENCES AND NOTES

1. D. L. Dixson, D. Abrego, M. E. Hay, Science 345 ,
   892 (2014).

10.1126/science.abo1771

Arctic change reduces

risk of cold extremes

In their Report “Linking Arctic variability

and change with extreme winter weather

in the United States” (3 September 2021,

p. 1116), J. Cohen et al. explain how the

combination of amplified Arctic warm-

ing and increased high-latitude snow

cover disrupts the stratospheric polar

vortex, which in turn drives severe winter

weather in mid-latitudes. They infer that

through this mechanism, Arctic change

has caused an increase in cold extremes

over the United States. However, this

inferred connection is not confirmed

by their analyses, and the increase

in extreme cold is contradicted by

past work.

Cohen et al.’s Report lacks analysis

of the observed trends in winter cold

extremes that have coincided with recent

rapid Arctic warming. Studies have

shown that winter cold extremes over the

United States are becoming less frequent

and less severe ( 1 – 6 ). These cold extremes

are warming faster than the average

temperature as day-to-day temperature

variability decreases ( 5 – 7 ). Climate model

experiments robustly show that Arctic

warming contributes to this reduction

in variability and cold extremes because

when Arctic air spills into lower latitudes,

this air is not as cold as it used to be

Edited by Jennifer Sills

Ducipsap erspelit ut faccat as nobit vitiunt et

LETTERS magniam volorro rercili quost, sandit is quasint

Polar vortices can cause severe winter weather, such as this February 2021 snowstorm in New York City.