Climate Pact Clinched

Global average carbon dioxide levels in the atmosphere inched past 400 ppm in early 2015. That and other scientific information turned up the heat on governments for collective action to fend off anthropogenic climate change. To that end, United Nations talks culminated earlier this month in a new global agreement intended to slow and eventually ramp down societies’ greenhouse gas emissions.

The global average atmospheric concentration of CO₂ surpassed 400 ppm in March, according to the National Oceanic & Atmospheric Administration’s Global Greenhouse Gas Reference Network. Scientists estimate that atmospheric levels of CO₂ haven’t been that high since a warm period some 4.5 million years ago.

Meanwhile, governments drew up a new global agreement on climate change that involves emission controls by all countries. As part of that deal, reached in Paris on Dec. 12, 185 nations and the European Union each made a pledge individually on how they will put the brakes on their greenhouse gas emissions. If countries keep those promises, global average temperatures are estimated to climb to nearly 3 °C above preindustrial levels by 2100, according to several analyses.

The final pact aims to hold global average temperatures to “well below” a 2 °C rise by 2100. It also includes a call “to pursue” efforts that might limit the rise to 1.5 °C. That more ambitious target was sought by low-lying island nations that likely would be inundated by sea-level rise due to warming and poor African countries projected to experience more intense droughts and flooding due to climate change.

To get to the 2 °C target the agreement calls for countries to revisit their emission-control pledges every five years. The hope is for governments to scale up those promises by curtailing emissions even more over time as technology for renewable energies and carbon capture and sequestration improves and becomes cheaper.

The pact also calls for governments to provide international funding to help developing countries reduce emissions and adapt to the impacts of climate change.