Global Climate Report - August 2019
Global Annual Temperature Rankings Outlook
« Global Climate Report - August 2019
- 2019 year-to-date temperatures versus previous years
- Global Annual Temperature Rankings Outlook
- Monthly temperature anomalies versus El Niño
- Mean Monthly Temperature Records Across the Globe
Global Annual Temperature Rankings Outlook
Overview
This outlook product, which will be updated monthly, provides a range of possibilities for the global annual temperature ranking at year's end, as well as a preliminary indication of next year's possible ranking. The calculation does not use any weather or climate forecast models. Rather, we utilize simulations of possible outcomes based on how widely the global temperature time series has varied from month to month in the historical record. Once we've created these plausible scenarios, we identify the 95% range of most likely outcomes.
Methodology
The key drivers for the calculation are 1) the difference, or separation, between recent monthly readings versus all previous annually-averaged values and 2) the statistical distribution of month-to-month fluctuations in the historical record. We utilize the operational version of the monthly global land and ocean NOAAGlobalTemp time series from January 1975–present. We utilize this time period because it provides a 40+ year baseline for estimating month-to-month fluctuations that are likely to be representative of real-time fluctuations. Next, we remove an ordinary least squares trend and simulate plausible outcomes based on autoregressive modeling of the residual time series. Finally, we add back in the trend as extended to account for simulated months, compute annual averages, and compare them to all prior annual averages since 1880 to arrive at annual rankings. This process is repeated 10,000 times, and we report the two-tailed 95% confidence interval. This methodology is analogous to an earlier analysis used to characterize whether a year would go on to become the warmest year on record. We anticipate that a future version of this product will account for statistical relationships between El Niño-Southern Oscillation (ENSO) indices and global temperatures.
The 2019 global annual temperature ranking outlook
Simulated ranking probabilities for 2019 global annual land and ocean temperature. Tick marks denote increments of 5% probability
Based on current anomalies and historical global annual temperature readings, it appears that it is virtually certain that 2019 will be a top 10 year, consistent with a strong propensity since 1988 for recent years to be initially ranked as a top 10 year (Sánchez-Lugo et al., 2018). Our calculations suggest:
- 0.3% chance of warmest year
- > 99.9% chance of a top 5 year
- > 99.9% chance of a top 10 year
- 95% confidence interval of 2nd to 4th warmest year on record
For Further Reading:
Sánchez-Lugo, A., C. Morice, P. Berrisford, and A. Argüez, 2018: [Global Climate] Global Surface Temperatures [in "State of the Climate in 2017"]. Bull. Amer. Meteor. Soc., 99, S11-S13.
Somewhat. Very. Extremely. How likely is it that 2015 will be the new warmest year on record?