What question did this study set out to answer?

To assess the primary causes of Northern Hemisphere temperature variability over the past 1,000 years and evaluate whether modern warming exceeds historical natural variations.

July 14, 2000Science

Causes of Climate Change Over the Past 1000 Years

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TCThomas J. CrowleyRutgers Sexual and Reproductive Health and Rights

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Implication

Climate modeling analysis demonstrates that late-twentieth-century warming exceeds natural variability over the past millennium, highlighting greenhouse gases as the dominant driver.

Key Points

To assess the primary causes of Northern Hemisphere temperature variability over the past 1,000 years and evaluate whether modern warming exceeds historical natural variations.
Compared Northern Hemisphere temperature reconstructions covering the past 1,000 years with simulations from an energy balance climate model.
Evaluated natural climate forcings, specifically solar irradiance and volcanism, against anthropogenic greenhouse gas forcing by comparing residual time series to coupled model control runs.
Natural forcings (solar irradiance and volcanic activity) accounted for 41% to 64% of preanthropogenic (pre-1850) decadal-scale temperature variations.
Isolating greenhouse gas forcing produced a late-20th-century warming signal that closely aligned with model predictions, indicating anthropogenic warming has exceeded natural climate variability.
Projected 21st-century temperature increases significantly surpass the natural variability of the past 1,000 years and exceed estimates for the last interglacial period.

Cite This Study

Thomas J. Crowley (2000) studied this question.

synapsesocial.com/papers/6a101c0ffa36b6e053fd40fd https://doi.org/10.1126/science.289.5477.270

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Implication

Climate modeling analysis demonstrates that late-twentieth-century warming exceeds natural variability over the past millennium, highlighting greenhouse gases as the dominant driver.

Causes of Climate Change Over the Past 1000 Years

Discussion

Member takes

Implication

Key Points

Cite This Study

Causes of Climate Change Over the Past 1000 Years

Discussion

Member takes

Implication

Key Points

Cite This Study

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