Global temperature range
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Global Average Temperature and Its Range
The annual average surface temperature of the world is about 14.0°C, with the Northern Hemisphere averaging 14.6°C and the Southern Hemisphere 13.4°C. The global mean temperature follows a seasonal cycle, peaking at 15.9°C in July and reaching a minimum of 12.2°C in January, reflecting the influence of the land-dominated Northern Hemisphere on global averages .
Historical Changes in Global Temperature
Over the past 150 years, global surface temperatures have increased, with notable warming periods between 1925–1944 and 1978–1997, during which global temperatures rose by 0.37°C and 0.32°C, respectively . Since the late 19th century, the global temperature has increased by approximately 1.2°C, with the six warmest years on record occurring between 2015 and 2020 .
Diurnal Temperature Range (DTR) Trends
Long-Term DTR Decline
The diurnal temperature range (DTR)—the difference between daily maximum and minimum temperatures—has generally decreased over the past century. From 1901 to 2014, the global land surface DTR declined at a rate of about -0.036°C per decade, with the most significant decreases occurring from the 1950s to the 1980s, especially in Asia and Africa Sun2018Xu2025Easterling1997+1 MORE. This decline is mainly due to minimum temperatures rising faster than maximum temperatures, a trend observed in most regions Vose2005Karl2017.
Recent Reversal and Regional Variations
However, recent decades have seen a reversal in this trend. Since the 1980s, and particularly after 1998, the global DTR has started to increase, especially in Europe, North America, and the Southern Hemisphere, at rates up to 0.136°C per decade Xu2025Huang2023. The increase in DTR in the past four decades is mainly due to a faster rise in daily maximum temperatures . Despite this, the overall long-term trend remains a net decrease in DTR since 1900 Sun2018Xu2025Easterling1997.
Factors Influencing DTR
Changes in DTR are influenced by several factors, including greenhouse gas emissions, atmospheric aerosols, cloud cover, and precipitation. Greenhouse gases are the dominant driver of the observed DTR decline, while aerosols have regionally variable effects—decreasing DTR in Asia but increasing it in Europe Easterling1997Liu2022. Increased cloudiness and precipitation are also linked to reduced DTR, particularly in the Northern Hemisphere Sun2018Easterling1997Karl2017.
Projected Future Global Temperature Range
Looking ahead, projections suggest that global temperatures are likely to increase by 2.0–4.9°C by 2100, with a median estimate of 3.2°C, under current emission trends. Achieving less than 2°C warming is considered unlikely without much faster reductions in carbon intensity .
Conclusion
The global temperature range, both in terms of annual averages and daily extremes, has undergone significant changes over the past century. While the long-term trend has been a narrowing of the diurnal temperature range due to faster increases in minimum temperatures, recent decades have seen a partial reversal with increasing DTR in some regions. These changes are closely linked to human activities, especially greenhouse gas emissions, and have important implications for climate and weather patterns worldwide Jones1999Sun2018Vose2005+7 MORE.
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