Predicted chance that global warming will temporarily exceed 1.5 °C

The Paris Agreement calls for efforts to limit anthropogenic global warming to less than 1.5 degrees C above preindustrial levels. However, natural internal variability may exacerbate anthropogenic warming to produce temporary excursions above 1.5 degrees C. Such excursions would not necessarily exceed the Paris Agreement, but would provide a warning that the threshold is being approached. Here we develop a new capability to predict the probability that global temperature will exceed 1.5 degrees C above preindustrial levels in the coming 5 years. For the period 2017 to 2021 we predict a 38% and 10% chance, respectively, of monthly or yearly temperatures exceeding 1.5 degrees C, with virtually no chance of the 5-year mean being above the threshold. Our forecasts will be updated annually to provide policy makers with advanced warning of the evolving probability and duration of future warming events.

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Author Smith, D. M.
Scaife, A. A.
Hawkins, E.
Bilbao, R.
Boer, G. J.
Caian, M.
Caron, L.
Danabasoglu, Gokhan
Delworth, T.
Doblas-Reyes, F. J.
Doescher, R.
Dunstone, N. J.
Eade, R.
Hermanson, L.
Ishii, M.
Kharin, V.
Kimoto, M.
Koenigk, T.
Kushnir, Y.
Matei, D.
Meehl, Gerald A.
Menegoz, M.
Merryfield, W. J.
Mochizuki, T.
Müller, W. A.
Pohlmann, H.
Power, S.
Rixen, M.
Sospedra-Alfonso, R.
Tuma, M.
Wyser, K.
Yang, X.
Yeager, Stephen
Publisher UCAR/NCAR - Library
Publication Date 2018-11-16T00:00:00
Digital Object Identifier (DOI) Not Assigned
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Resource Version N/A
Topic Category geoscientificInformation
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Metadata Date 2025-07-11T19:33:28.426263
Metadata Record Identifier edu.ucar.opensky::articles:22204
Metadata Language eng; USA
Suggested Citation Smith, D. M., Scaife, A. A., Hawkins, E., Bilbao, R., Boer, G. J., Caian, M., Caron, L., Danabasoglu, Gokhan, Delworth, T., Doblas-Reyes, F. J., Doescher, R., Dunstone, N. J., Eade, R., Hermanson, L., Ishii, M., Kharin, V., Kimoto, M., Koenigk, T., Kushnir, Y., Matei, D., Meehl, Gerald A., Menegoz, M., Merryfield, W. J., Mochizuki, T., Müller, W. A., Pohlmann, H., Power, S., Rixen, M., Sospedra-Alfonso, R., Tuma, M., Wyser, K., Yang, X., Yeager, Stephen. (2018). Predicted chance that global warming will temporarily exceed 1.5 °C. UCAR/NCAR - Library. https://n2t.org/ark:/85065/d77p92cc. Accessed 02 December 2025.

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