IPCC Fourth Assessment Report Summary for Policymakers Released: February 2, 2007

On February 2, 2007, the Intergovernmental Panel on Climate Change (IPCC) released the Summary for Policymakers of its Fourth Assessment Report (AR4) in Paris, France. This document represented a pivotal moment in the global understanding of climate change. It provided unequivocal evidence that the Earth’s climate system is warming and clearly identified human activities as the primary driver.

Key Findings

1. Undeniable Warming: The report presented robust and compelling evidence demonstrating that the Earth’s climate system had been warming over the previous century. It was noted that eleven of the twelve years from 1995 to 2006 ranked among the 12 warmest years on record since 1850.

2. Human Influence: For the first time, the IPCC stated with over 90% confidence—reflected in the terminology “very likely”—that human activity, particularly the emission of greenhouse gases from burning fossil fuels, deforestation, and other industrial activities, had been the dominant cause of observed warming since the mid-20th century.

3. Future Projections: The report included projections suggesting that continued greenhouse gas emissions at or above current rates would cause further warming and induce many changes in the global climate system during the 21st century that would very likely be larger than those observed during the 20th century.

4. Impacts on Natural Systems: Observations showed many natural systems were already being affected by regional climate changes, particularly temperature increases. Examples included the earlier timing of spring events, such as leaf-flushing in plants, and shifting ranges for animal species.

Context and Significance

The Fourth Assessment Report was the culmination of years of research and analysis by hundreds of scientists worldwide. It built upon previous assessments and integrated new scientific knowledge gained over the past five years. The report played a critical role in enhancing public and governmental understanding of climate change, driving international policy discussions, and shaping frameworks like the Kyoto Protocol and subsequent international agreements.

Aftermath and Consequences

The release of the AR4 fundamentally altered the global discourse on climate action. It provided a scientific basis for policies aimed at mitigating climate change and adapting to its inevitable effects. In response to the report, many countries reevaluated their climate policies, aiming to reduce emissions and invest in renewable energy sources.

The AR4 also catalyzed broader recognition of the need for collective global action, laying the groundwork for future international negotiations including the Paris Agreement of 2015. Its findings continue to influence research, policy, and public awareness in the realm of climate science and environmental responsibility.