When did global warming begin
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The Onset of Global Warming: A Historical Perspective
Early Indicators of Global Warming in the 19th Century
The onset of global warming can be traced back to the mid-19th century. Research indicates that sustained industrial-era warming of the tropical oceans and Northern Hemisphere continents began during this period, driven by greenhouse gas emissions from industrial activities2. This early warming was nearly synchronous across these regions, suggesting a significant anthropogenic influence on the climate even before the 20th century2.
The Early 20th Century Warming (ETCW)
The first half of the 20th century saw a pronounced warming period known as the Early Twentieth Century Warming (ETCW). This period, spanning from 1901 to 1950, was characterized by significant temperature increases, particularly in the Arctic3. Studies attribute approximately half of this warming to a combination of increasing greenhouse gases and natural forcing, with the remainder influenced by internal climate variability3 4. This period also included notable climatic events such as the "Dust Bowl" droughts in North America and extreme heat waves3.
Mid-20th Century to Present: Accelerated Warming
The most significant and well-documented phase of global warming began in the mid-1970s. This period saw a marked increase in global mean surface temperatures, largely attributed to human-induced greenhouse gas emissions1 9. Despite a perceived hiatus in the early 2000s, the overall trend of rising temperatures has continued, with more than 90% of the excess heat being absorbed by the oceans1. This ongoing warming has been accompanied by melting ice caps and rising sea levels, further evidencing the persistent nature of global warming1.
Pre-Industrial Contributions to Global Warming
Interestingly, some hypotheses suggest that human activities may have influenced the climate long before the industrial era. Evidence from Antarctic ice cores indicates that early agricultural practices, such as rice farming and forest clearance, began emitting significant amounts of greenhouse gases as early as 5000 years ago7 8. These early emissions may have contributed to a gradual warming trend, although the most substantial impacts have been observed since the onset of the industrial revolution7.
Conclusion
In summary, global warming began to manifest significantly in the mid-19th century with the advent of industrial activities. The early 20th century experienced notable warming, influenced by both anthropogenic and natural factors. The most pronounced and sustained warming, however, has occurred since the mid-1970s, driven primarily by human-induced greenhouse gas emissions. Understanding these historical trends is crucial for predicting future climate changes and mitigating their impacts.
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Most relevant research papers on this topic
An apparent hiatus in global warming?
Global warming has not stopped; it is merely manifested in different ways, with sea-level rise being more relentless.
Highly CitedEarly onset of industrial-era warming across the oceans and continents
Industrial-era warming began in the mid-19th century, with tropical oceans warming first and Northern Hemisphere warming nearly synchronously.
Rigorous JournalHighly CitedThe early 20th century warming: Anomalies, causes, and consequences
The Early Twentieth Century Warming (ETCW) was driven by a combination of greenhouse gases and natural forcing, with aerosols playing a minor role, and included exceptional events like the Dust Bowl droughts and European droughts.
Literature ReviewHighly CitedSimulation of early 20th century global warming
Early 20th century global warming may have been caused by a combination of human-induced radiative forcing and unusually large internal ocean-atmosphere variability.
Highly CitedGlobal warming: How skepticism became denial
The public's denial of global warming stems from a professional public relations effort driven by industrial and ideological concerns, and scientists need to mount a concerted public relations campaign to restore trust.
Global warming in an independent record of the past 130 years
The Paleo Index shows a significant upward trend in global temperature from 1880 to 1995, similar to the Global Surface Temperature Time Series, with a small trend from 1730-1929.
The Anthropogenic Greenhouse Era Began Thousands of Years Ago
The anthropogenic greenhouse era began thousands of years ago, with early agriculture in Eurasia contributing to global warming and forest regrowth during the Little Ice Age.
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