Decades of research continue to strengthen the certainty that human activity drives the rapid climate change that is already happening. The natural “greenhouse effect” has been established for centuries, and the carbon cycle is well-understood.
The natural cycle of CO2 and other greenhouse gasses warms the atmosphere allowing life on Earth to flourish. The question for scientists–for all of us–is climate sensitivity.
Climate sensitivity refers to the extent to which rising levels of greenhouse gases affect the Earth’s temperature. It is typically defined as the global temperature rise following a doubling of CO2 concentration in the atmosphere compared to pre-industrial levels.
Since the start of the industrial revolution, atmospheric CO2 concentrations have risen more than 50 percent, from 280 parts per million to 424 ppm, and climbing.
Modeling the climate is difficult. Scientists were concerned their early models didn’t fully account for feedback loops, like changing cloud cover, sea ice, permafrost, and water vapor.
These positive feedback loops can amplify the warming effect of increased greenhouse gas concentrations. When these feedback loops can reach a threshold—their tipping point—beyond which is systemic change.
A New Normal
If, for example, warmer temperatures in the Arctic cause permafrost to melt and release methane, a potent greenhouse gas, warming the atmosphere further, causing more permafrost to melt. The cycle feeds on itself and grows. Permafrost is only one ongoing feedback loop impacting the range and pace of climate change.
Each reinforcing loop interacts with the other in ways scientists work to understand better. Pinpointing where their tipping points lay is uncertain. What is certain is our inexorable march toward them.
Decades of continually rising emissions from burning fossil fuels have altered atmospheric and ocean chemistry. As climate science advances and measurements become more detailed and granular, the evidence reveals that anthropogenic climate change is a clear and present danger.
Learn about climate science, the causes and impacts of global warming, and the potential future scenarios depending on our actions.
