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🌡️intro to climate science review

Fifth Assessment Report

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

The Fifth Assessment Report (AR5) is a comprehensive evaluation of climate science published by the Intergovernmental Panel on Climate Change (IPCC) in 2013 and 2014. It presents the current state of knowledge regarding climate change, including its causes, impacts, and potential future risks. AR5 emphasizes the significance of climate sensitivity and the inherent uncertainties in projections, providing a framework for policymakers and scientists to understand how climate change may affect the planet in the coming years.

5 Must Know Facts For Your Next Test

  1. The Fifth Assessment Report is divided into three working group contributions: the physical science basis, impacts, adaptation, and vulnerability, and mitigation of climate change.
  2. AR5 highlighted that global surface temperatures have risen significantly since the late 19th century, primarily due to human activities, particularly greenhouse gas emissions.
  3. The report indicates that there is high confidence that continued warming will lead to more extreme weather events, sea level rise, and shifts in ecosystems.
  4. AR5 introduced updated estimates for climate sensitivity, suggesting that it is likely between 1.5°C and 4.5°C for a doubling of CO2 concentrations, with an even chance that it could be higher.
  5. The uncertainties in climate projections discussed in AR5 arise from limitations in models, natural variability, and unknown feedback mechanisms within the climate system.

Review Questions

  • How does the Fifth Assessment Report address the concept of climate sensitivity and its importance in understanding future climate projections?
    • The Fifth Assessment Report discusses climate sensitivity as a critical factor in determining how much global temperatures will rise with increased levels of carbon dioxide. It provides updated estimates on climate sensitivity, suggesting a likely range between 1.5°C and 4.5°C for doubled CO2 concentrations. This understanding is essential because it influences predictions about future warming and informs policymakers about potential risks associated with different greenhouse gas emission scenarios.
  • Evaluate the implications of the uncertainties presented in the Fifth Assessment Report for climate change mitigation strategies.
    • The uncertainties highlighted in the Fifth Assessment Report present significant challenges for climate change mitigation strategies. They stem from model limitations, natural climate variability, and unknown feedbacks within the system. Policymakers must consider these uncertainties when developing strategies, as they affect risk assessment and planning. This means adopting flexible approaches that can be adjusted as new data becomes available or as models improve over time.
  • Synthesize the key findings of the Fifth Assessment Report regarding the impacts of climate change and their implications for global policy-making.
    • The Fifth Assessment Report synthesizes crucial findings that illustrate the widespread impacts of climate change, including increased frequency of extreme weather events, rising sea levels, and ecological shifts. These findings emphasize the urgency for global policy-making to prioritize emission reductions and adaptation measures. By presenting clear evidence linking human activities to climate change impacts, AR5 serves as a critical tool for negotiators in international agreements like the Paris Agreement, pushing for comprehensive actions to mitigate risks associated with a warming planet.