Climate change science is an incredible mix of systems across time and space
When it comes to climate change science, people often fail to see the forest for the trees. With a complex array of variables like cloud patterns, ocean circulation, solar cycles, volcanic eruptions, and more, the climate system requires a tremendous degree of perspective across time and space and is therefore very difficult to observe. Without this perspective, we tend to focus on specific weather events or short-term trends that do not necessarily represent the overall climate pattern. It has fallen upon climate scientists to develop the technical sophistication and to employ the research methods necessary to understand climate variables, how they change across time and space.
The hottest decade: Overcoming natural cooling factors
Looking at the complete global picture, one that includes ocean heat content as well as surface and atmospheric warming trends, what we find is striking. Not only is global warming still rising, but recent temperatures are also unprecedented at a time when natural indicators alone promote cooling.
Thirteen out of fifteen of the hottest years on record occurred since 2000, and the two exceptions (1997 and 1998) were strong El Niño years. The decade from 2001-2010 was the warmest since thermometer records began in 1850 and probably going back further. Temperature reconstructions dating back 11,000 years show that modern temperatures are among the warmest human civilization has ever experienced, and that the modern rate of warming is exceptional, likely unprecedented in that time period.
The natural factors that should have been cooling the planet, if not for human influence, include:
- Two La Niñas: New research indicates that these cooling cycles may be working to sequester heat in the deep ocean.
- A deep solar minimum: This is part of a recurring cycle of reduced solar activity that results in less heat reaching the Earth.
- Aerosol pollution: Energy production in developing countries as well as volcanic eruptions reflect solar radiation back into space.
Rather than letting wishful thinking convince us that surface warming has “paused,” we should be asking: how much warming will we see, as we continue to pump more and more carbon into the atmosphere and the planet’s natural cooling effects cease?
In the approximately 150 years since we began measuring surface temperatures with thermometers, temperatures haven’t risen upwards smoothly – they’ve moved in a staircase pattern, with “steps” lasting a decade or more. History tells us that once current natural cycles revert, surface warming will jump upward (as it did in 1998). This shows us the true and sobering fingerprint of human influence.