Editorial by Achim Steiner, UN Under Secretary General and Executive Director, United Nations Environment Programme (UNEP)
The science of climate change has advanced dramatically since the Intergovernmental Panel on Climate Change (IPPC) published its first assessment report seventeen years ago.
The evidence available to researchers – from ice cores and other residue of ancient climates to 21st century satellite measurements – has grown exponentially. Dramatic upgrades in computer power combined with increasingly robust theory have provided new insights into how the oceans and the atmosphere respond to rising levels of greenhouse gases.
Thanks to the rapid progress in climate modeling and data collection and analysis, the IPCC’s newest assessment report on the physical basis of climate change, released today in Paris, concludes that scientists now have very high confidence that human activities have caused the global climate to warm over the past 250 years.
The scientific method that has made this progress possible is one of humanity’s most impressive cultural achievements. By gathering and analyzing evidence, developing hypotheses and designing experiments to test them, scientists have unlocked many of nature’s most closely held secrets. The spirited and sometimes intemperate debate amongst competing theories and research teams reflects the vitality of this search for truth and knowledge.
The particular contribution of the IPCC has been to render the values-neutral domain of science more accessible to the values-based world of policy. The IPCC does not conduct new research. Instead, its mandate is to make policy-relevant assessments of the existing worldwide literature on the scientific, technical and socio-economic aspects of climate change. The IPCC’s multi-volume assessment reports of 1990, 1996 and 2001 played a major role in inspiring governments to adopt and implement the United Nations Framework Convention on Climate Change and the Kyoto Protocol.
Policy on a complex and high-stakes challenge like climate change must be based on sound science. The IPCC has demonstrated that it is possible for scientists to agree on the state of knowledge about climate change and then – a crucial next step – to communicate this understanding to policymakers. Once this difficult and time-consuming process has been accomplished, a separate policy debate based on agreed science, but driven by values and interests, can commence.
Positioned at the nexus between science and policy, the IPCC follows procedures that are acceptable to both the science and policy communities. It emphasizes rigour, transparency and inclusiveness. Its assessments are carefully reviewed by experts as well as by governments. The scale of the IPCC’s achievement in examining thousands of studies and articles in peer-reviewed scientific journals, engaging some 2,000 scientists from across the globe, and achieving broad agreement amongst both experts and governments on the fundamental points of climate science is nothing short of impressive.
Today’s IPCC report confirms that the climate is already changing and that warming is likely to accelerate over the course of this century. Important uncertainties remain – notably about the respective roles of clouds, ice caps, oceans and deforestation – but the overall message is clear. There can no longer be any serious doubt that humanity’s emissions of carbon dioxide, methane, nitrous oxide and other greenhouse gases pose a very real risk to our well-being, and that children born in 2007 will live in a warmer world of greatly altered weather patterns and higher sea levels.
How should we respond to these findings? Scientists themselves will interpret the policy implications of their findings in different ways. My view is based on my own values: that we must act as responsible stewards of this planet, respect the rights of others, including future generations, and take precautions against potentially large risks even in the face of uncertainty or the absence of absolute certainty.
The scientists have done their job. It is now up to governments, and indeed everyone of us, to transform their comprehensive and incontrovertible findings into public policy.
The IPCC was established in 1988 by the World Meteorological Organization and UNEP.