Science tells us that the climate is changing, primarily caused by human activities that emit CO2. California has been a leader in responding to climate change by implementing greenhouse gas mitigation policies to reduce CO2 emissions, thereby reducing climate change impacts. Unfortunately, the majority of the rest of the world is not taking action to curb CO2 emissions. Because CO2 emissions continue to increase, the need for climate adaptation planning (or, how do we plan and respond to the coming climate impacts associated with a warmer world) is necessary. Mitigating policies to reduce CO2 emissions are no longer sufficient to address future climate change. That future is now here.

In November 2014, the Intergovernmental Panel on Climate Change (IPCC) completed its Fifth Assessment Report (AR5) with the release of its Synthesis Report. AR5 represents the current consensus on knowledge about climate change and is a collaborative effort of hundreds of climate scientists led by the IPCC. Initiated in 1988, reports issued by the IPCC have grown more certain of the causality of climate change and more urgent need to address it. In AR5, the IPCC reports that:

“Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased.”

The AR5 report also indicates that:

“the atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years. Carbon dioxide concentrations have increased by 40% since pre-industrial times, primarily from fossil fuel emissions and secondarily from net land use change emissions.”

To put a visual to that statement, the graph below from the National Oceanic and Atmospheric Administration (NOAA) shows what CO2 levels in the atmosphere have looked like over the last 800,000 years. The graph also includes future low and high emissions projections.

Continued measurements by the World Meteorological Organization indicate the CO2 concentrations continue to rise annually by approximately 3 ppm to a record level in 2013 of 396 ppm (locking in approximately 0.8 degrees celsius increase in temperatures over preindustrial levels). The widely politically supported 2 degrees celsius, the threshold beyond which catastrophic consequences are believed to occur, equates to approximately 450 ppm CO2. If the current rate of increase stays constant, we will exceed 450 ppm in 18 years (around 2032).

There is growing evidence that the 2 degrees celsius threshold is beyond a safe level and that extreme weather has already begun. The 2014 National Climate Assessment reports that “over the last 50 years, much of the U.S. has seen increases in prolonged periods of excessively high temperatures, heavy downpours, and in some regions, severe floods and droughts.” Extreme weather, unfortunately, is only one consequence. Sea level rise, ocean acidification and melting of the polar ice caps and world’s glaciers, to name a few, are also expected to occur.

Which leads us to this statement by the IPCC:

“Without additional mitigation efforts beyond those in place today, and even with adaptation, warming by the end of the 21st century will lead to high to very high risk of severe, widespread, and irreversible impacts globally (high confidence).”

In other words, it’s time to get serious about mitigation and adaptation.