Monday, February 7, 2011

Thoughts on the relationship between weather, climate, and global warming

After last week's snow storm there was a lot of noise about whether this was caused by climate change, whether it refuted global warming, or if it was just weather in the Midwest. This brought me back to how much difficulty there is in understanding the relationship between weather, climate change and global warming. Without getting into whether we are observing a natural or man-made phenomena, I am going to take a stab at this clarifying these relationships.

  • The underlying phenomena driving climate change is global warming – the Earth is heating up. This is a simple, verifiable fact.
  • This heating occurs unevenly, largely do to local and regional variables, (e.g., air and ocean currents, atmospheric moisture, relative albedo, carbon sequestration, urban heat islands, etc.).
  • As the Earth gets warmer, ocean and air currents change, distributing heat and moisture in new patterns. Warmer oceans also mean more moisture is available to the atmosphere.
  • We experience these changes in our daily lives through weather, which is highly sensitive to such forcings.
  • Over longer periods, these effects produce changes in climate, which can dramatically alter the physical and biological characteristics of place on local, regional and global scales.
  • These changes in climate can also create feedback that amplifies these effects locally, regionally and globally.
More concisely, the warming of the planet causes changes in distribution of heat and moisture through weather. These patterns, sustained over time, cause changes in climate. Changes in climate in turn can create feedback that further impacts weather patterns.

And so on...

When we talk about the response of weather to global warming, we are talking about a large and nonlinear system (weather) responding to an influx of additional energy (global warming). Even though the increase in energy input may be gradual and seemingly small, the system response can be chaotic and severe.

By itself, the storm tells us very little about global warming and climate change. However, as part of a larger pattern of increasingly severe and unusual storms, heat-waves, droughts, and floods - all set against a background of record setting global temperatures - last weeks storm is entirely consistent with what we should be expecting to see. That is, just about anything.

As an added note, evidence suggests that historically, dramatic shifts in global climate have not tended to occur gradually, but quite often occur in time periods as short as a decade or less. Again, this is not inconsistent with non-linear systems.


  1. Well said. One added benefit to us doing our project is that we will be educating young people, using real data, about global warming and climate change. We need to get the word out in the form of pictures of glaciers shrinking, sea ice disappearing and average global temperatures rising etc... The evidence in support of global warming is not refutable. I think the only agreed upon unknown is that no one really knows how fast things will change if we continue on the path we are currently on or what the final chapter will be. Students do not read science articles or watch documentaries and know very little about
    what is happening with the climate. We as educators need to be the ones to bring the message to them so that they grow up understanding what many adults
    currently misunderstand.

  2. One of the questions I get asked lots by my sixth grade class is "What was the weather like when you were a kid?" When I think about my childhood I remember really bitterly cold winters, somewhat similar to what we have today. What is different, I think, is Fall. I don't remember October being as warm. I cannot remember having weather close to 32C in October as we have had in the last several years. I wonder if this is my faulty memory or if this is a change in the regions seasonal pattern.