Global warming trends
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Global Warming Trends: Surface Temperature and Beyond
Global Surface Temperature Increases
Research consistently shows that the Earth has warmed significantly since the preindustrial era, with estimates indicating a rise of about 1.2 ± 0.1 °C globallySong2022Mohorji2017. Analyses of long-term temperature records reveal that this warming has been steady since the 1970s, with no statistically significant slowdown or acceleration outside of expected short-term variabilityRahmstorf2017Ji2014. The warming trend is evident in both land and ocean surface temperatures, with global land surface air temperature showing noticeable increases, especially since the 1980sJi2014Mohorji2017.
Regional Variability and Arctic Amplification
Warming is not uniform across the globe. The Arctic region, in particular, has experienced much faster warming than the global average—up to 2.5–2.8 times higher in recent decadesWang2022Huang2017. This Arctic amplification has contributed significantly to the overall global warming trend, and when properly accounted for, it eliminates the notion of a recent "hiatus" or slowdown in global warming. Other regions, such as Europe and Russia, have also shown statistically significant warming, while the fastest warming in recent decades has occurred in the northern mid-latitudesJi2014Wang2022.
Comprehensive Metrics: Beyond Surface Air Temperature
While surface air temperature (SAT) is the most common metric for tracking global warming, it does not capture the full picture. Including humidity through the surface equivalent potential temperature (Thetae_sfc) provides a more comprehensive measure. From 1980 to 2019, Thetae_sfc increased by 1.48 °C globally—almost double the SAT increase—due to rising atmospheric humidity and latent energy. This metric also correlates more strongly with trends in heat extremes and extreme precipitation, especially in the tropics.
Trends in Extreme Weather and Climate Events
The most robust global changes in climate extremes are found in the frequency and duration of heatwaves, which have increased in recent decadesSong2022Alimonti2022. However, trends in the intensity of heatwaves, daily precipitation extremes, and tropical cyclones are less clear or show substantial variability. Some studies suggest that, while temperature extremes are increasing, other extreme weather indicators such as floods, droughts, and crop yields do not yet show clear global trends attributable to warming. Nevertheless, projections indicate that, under high-emissions scenarios, large parts of the tropics and subtropics will experience strong increases in temperature and precipitation extremes in the coming decades.
Future Projections and Model Constraints
Recent climate models (CMIP6) project a range of future warming scenarios. However, models that simulate much stronger future warming often do not align with observed trends from recent decades. By constraining projections with observed warming, the likely range of future warming is reduced, making it more consistent with previous assessments and the targets of the Paris AgreementTokarska2020Liang2020. Under high emissions, global mean surface air temperature could rise by several degrees by 2100, with even larger increases in heat extremes and extreme precipitation if greenhouse gas emissions are not curbedSong2022Tokarska2020Liang2020.
Conclusion
Global warming is a well-established, ongoing trend, with the Earth’s surface temperature rising steadily over the past century. The warming is most pronounced in the Arctic and northern mid-latitudes, and is more comprehensively measured when humidity is included. While some extreme weather events, particularly heatwaves, are increasing in frequency and duration, other indicators show less clear trends. Future warming projections are best constrained by observed trends, underscoring the importance of continued monitoring and mitigation efforts.
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