Climate has changed throughout the 4.5 billion year history of the Earth. Today, the difference is that our planet is undergoing changes unprecedented in human history and, although changes as large as those we are witnessing now have occurred in the geological past, relatively few have happened with the speed that characterizes today's climate changes (current WMO Annual Climate Statement). WCRP research underpins understanding of fundamental changes including increasing concentrations of greenhouse gases, stratospheric ozone depletion (SPARC) and the changing chemical composition of the atmosphere and oceans (joint initiative between WCRP and IGBP chemistry). In addition to aerosol and greenhouse gas increases (Climate Change brochure), human activities are significantly influencing the Earth's environment in many ways. WCRP researches anthropogenic changes to Earth's land surface, to oceans, to biological diversity, to freshwater and its cycling and to biogeochemical cycles, particularly seeking differences from natural variability (25th Anniversary Brochure). Many of these changes are accelerating.

Over the last 15 or so years, with increased awareness of the potential impacts of climatic changes, there has been an evolving demand from policymakers for high quality climate predictions. The WCRP research underpins many international assessments, including those of the Intergovernmental Panel on Climate Change (IPCC), the Millennium Ecosystem Assessment and evaluations of research needs for the United Nations Framework Convention on Climate Change (UNFCCC). Global changes threaten the balance of climatic conditions under which life evolved and is sustained. The speed of changes now also threatens social and economic systems including agriculture, water supplies, coastal infrastructure and susceptibility to diseases (UNFCCC SBSTA 24 webcast). WCRP contributes to joint projects on water systems, carbon, food security and human health through the Earth System Science Partnership (ESSP).

More on WCRP's anthropogenic climate change activities.