What causes the seasons to change?

Introduction

The changing of seasons is a fundamental aspect of Earth's climate system, driven by various factors. Understanding the causes behind seasonal changes is crucial for climatology, agriculture, and ecological studies. This synthesis explores the primary drivers of seasonal changes, focusing on the Earth's axial tilt and the impact of climate change.

Key Insights

Earth's Axial Tilt:
- The primary cause of seasonal changes is the Earth's axial tilt in relation to its orbital plane around the Sun. This tilt causes different parts of the Earth to receive varying amounts of sunlight throughout the year, leading to the progression of seasons.
Impact of Climate Change:
- Lengthening of Growing Seasons:
  - Recent global warming has led to a lengthening of the growing season by approximately 10-20 days in the last few decades, with an earlier onset of spring being most prominent .
- Changes in Season Lengths:
  - Summer has increased in length, while winter has decreased, with spring and autumn also experiencing shifts. These changes are attributed to greenhouse warming and are expected to continue, potentially leading to summers lasting nearly half a year by 2100 .
- Regional Variability:
  - The changes in season lengths are more pronounced in drylands compared to humid lands, with significant variations in spring, summer, and autumn lengths in the Northern Hemisphere mid-latitudes.
- Phenological Shifts:
  - Changes in the timing of natural events, such as earlier spring onset and delayed autumn, are linked to increased temperatures. These shifts affect plant and animal ecosystems and have broader implications for carbon storage and climate feedbacks .
Meteorological and Astronomical Definitions:
- Traditional definitions of seasonality based on meteorological and astronomical criteria are insufficient to capture the rapid changes associated with climate change. New metrics using surface and tropospheric temperature analyses provide a more accurate assessment of seasonal transitions.

Conclusion

The primary driver of seasonal changes is the Earth's axial tilt, which dictates the amount of sunlight different regions receive throughout the year. However, climate change is significantly altering the length and timing of seasons, with notable extensions in the growing season and shifts in the onset of spring and autumn. These changes have profound implications for ecosystems, agriculture, and climate feedback mechanisms. Understanding these dynamics is essential for adapting to and mitigating the impacts of a changing climate.

What causes the seasons to change?

Summary

Introduction

Key Insights

Conclusion

Sources and full results

Reconsidering meteorological seasons in a changing climate

The length of summer has increased by an average of 13 days and winter has decreased by an average of 20 days, reflecting more substantial seasonal changes than previously studied due to anthropogenic climate change.

Growing season changes in the last century

A 10-20 day extension in the growing season has been observed in recent decades, likely due to global warming, potentially impacting plant and animal ecosystems and climate change.

Web Resources for the Seasons

The seasons are caused by the Earth's axial tilt in relation to the orbital plane of the Sun and Earth, not the Earth-Sun distance.

Projected Future Seasonal Changes in Tropical Summer Climate

Seasonal changes in tropical summer climate, driven by changes in trade winds and Hadley circulation, are projected to increase summer sea surface temperature and decrease winter sea surface temperature, affecting deep convection and precipitation.

Changing Seasons: An Effect of the North Atlantic Oscillation?

The North Atlantic Oscillation influences the onset of spring season in Europe, with warmer winters leading to earlier onsets of the growing season and impacting plant phenology and ecosystems.

Changes in lengths of the four seasons over the drylands in the Northern Hemisphere mid-latitudes

Drylands in the Northern Hemisphere mid-latitudes experienced enhanced changes in spring, summer, and autumn lengths due to global warming, with external forcing playing a stronger role than internal variability.

Changes in rainfall seasonality in the tropics

Climate change is altering rainfall seasonality in the tropics, with increased variability and shifts in magnitude, timing, and duration.

Changing Lengths of the Four Seasons by Global Warming

Global warming is projected to lengthen summer by nearly half a year and shorten winter by less than 2 months by 2100, causing disrupted agriculture seasons and increased risks to humanity.

Phenology Feedbacks on Climate Change

Climate warming has advanced biological spring and delayed biological winter, affecting ecological processes, agriculture, forestry, human health, and the global economy.

Observed changes in seasons: an overview

Climate change is leading to a delay in autumn, causing winter to be squeezed at both ends, increasing the growing season and affecting various species.

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