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Aerosol forcing of the position of the intertropical convergence zone since AD1550

Ridley, H.E.; Asmerom, Y.; Baldini, J.U.L.; Breitenbach, S.F.M.; Aquino, V.V.; Prufer, K.M.; Culleton, B.J.; Polyak, V.; Lechleitner, F.A.; Kennett, D.J.; Zhang, M.; Marwan, N.; Macpherson, C.G.; Baldini, L.M.; Xiao, T.; Peterkin, J.L.; Awe, J.; Haug, G.H.

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H.E. Ridley

Y. Asmerom

J.U.L. Baldini

S.F.M. Breitenbach

V.V. Aquino

K.M. Prufer

B.J. Culleton

V. Polyak

F.A. Lechleitner

D.J. Kennett

M. Zhang

N. Marwan

L.M. Baldini

T. Xiao

J.L. Peterkin

J. Awe

G.H. Haug



The position of the intertropical convergence zone is an important control on the distribution of low-latitude precipitation. Its position is largely controlled by hemisphere temperature contrasts1, 2. The release of aerosols by human activities may have resulted in a southward shift of the intertropical convergence zone since the early 1900s (refs 1, 3, 4, 5, 6) by muting the warming of the Northern Hemisphere relative to the Southern Hemisphere over this interval1, 7, 8, but this proposed shift remains equivocal. Here we reconstruct monthly rainfall over Belize for the past 456 years from variations in the carbon isotope composition of a well-dated, monthly resolved speleothem. We identify an unprecedented drying trend since ad 1850 that indicates a southward displacement of the intertropical convergence zone. This drying coincides with increasing aerosol emissions in the Northern Hemisphere and also marks a breakdown in the relationship between Northern Hemisphere temperatures and the position of the intertropical convergence zone observed earlier in the record. We also identify nine short-lived drying events since ad 1550 each following a large volcanic eruption in the Northern Hemisphere. We conclude that anthropogenic aerosol emissions have led to a reduction of rainfall in the northern tropics during the twentieth century, and suggest that geographic changes in aerosol emissions should be considered when assessing potential future rainfall shifts in the tropics.


Ridley, H., Asmerom, Y., Baldini, J., Breitenbach, S., Aquino, V., Prufer, K., …Haug, G. (2015). Aerosol forcing of the position of the intertropical convergence zone since AD1550. Nature Geoscience, 8(3), 195-200.

Journal Article Type Article
Acceptance Date Jan 2, 2015
Online Publication Date Feb 9, 2015
Publication Date Mar 1, 2015
Deposit Date Feb 10, 2015
Publicly Available Date Feb 24, 2015
Journal Nature Geoscience
Print ISSN 1752-0894
Electronic ISSN 1752-0908
Publisher Nature Research
Peer Reviewed Peer Reviewed
Volume 8
Issue 3
Pages 195-200


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