U.S. Climate Resilience Toolkit

The Working Group II contribution to the IPCC Sixth Assessment Report assesses the impacts of climate change, looking at ecosystems, biodiversity, and human communities at global and regional levels. It also reviews vulnerabilities and the capacities and limits of the natural world and human societies to adapt to climate change.

The Second State of the Carbon Cycle Report (SOCCR2) was led and developed by the Carbon Cycle Interagency Working Group under the auspices of the U.S. Global Change Research Program. Contributing to the Fourth National Climate Assessment, SOCCR2 is designed as a special interagency assessment focused on the advances in the science and the understanding of the carbon cycle across North America since the first SOCCR (2007). Specifically, SOCCR2 focuses on U.S. and North American carbon cycle processes, stocks, fluxes, and interactions with global-scale carbon budgets and climate change impacts in managed and unmanaged systems. The report includes an assessment of the carbon stocks and fluxes in soils, water (including near-coastal oceans), vegetation, aquatic-terrestrial interfaces (e.g., coasts, estuaries, wetlands), human settlements, agriculture, and forestry. It considers relevant carbon management science perspectives and science-based tools for supporting and informing decisions. The status of and emerging opportunities for improving measurements, observations, and projections of stocks and fluxes in the carbon cycle, including uncertainty identification, are part of the report.

This report documents that the average temperature in 2015 was over one degree higher than pre-industrial times and that the period 2011–2015 was the warmest five-year period on record, consistent with established warming trends. The report further documents that in 2015 another milestone was reached, with globally averaged CO₂ levels of 400 parts per million (ppm). The year 2016 is on track to be even warmer and will be the first year in which CO₂ at the Mauna Loa Observatory remains above 400 ppm all year, and for many generations to come.

The probability of extreme climate events since 2011, especially those involving extreme high temperatures, has been substantially increased by climate change, often by a factor of 10 or more. The single most significant event in humanitarian terms, with over 250,000 lives lost, was the 2011–2012 famine in the Horn of Africa, where drought was a major factor.