While Al Gore was receiving an Oscar last month in sunny southern California, bone-chilling cold still prevailed in much of the hinterlands. People could not be blamed for wondering how the cold temperatures conformed with the warm climate change hailed by the former Vice-President. That is a legitimate question but a standard answer may leave Americans puzzled.

In February, the Center for American Progress wrote on the distinction between weather and climate, pointing out the difference but then explaining how the current cold snap and snowstorms are “exactly what increasing greenhouse gas emissions predict.” Note the ascription of predictive powers to greenhouse gas emissions, an interesting concept in a realm associated with science. More important, this is precisely the sort of misleading two-sided analysis that confuses the issue of weather and climate change.

Weather is a short-term phenomenon, describing atmosphere, ocean, and land conditions hourly or daily.  Climate, on the other hand, is the long-term average of weather patterns, and includes larger- and longer-scale influences and feedbacks.  All of the weather in a region helps to define its climate, and changes to the climate impact weather; changes in climate can, for example, lead to dryer conditions over the long term, or cause higher average energy of ocean-based storm systems.

However, one cannot correlate individual weather events to changes in climate.  Climate patterns only unfold over long periods of time.  It is difficult to know whether or not any effects are seen when looking at a single event or a single season.  In fact, some extreme weather events are very difficult to link to climate at all. 

Weather observations have indicated that the frequency of heavy precipitation events has likely increased over most land areas. As noted, however, in the recent summary assessment by the Intergovernmental Panel on Climate Change (IPCC), there is not enough evidence to determine whether or not there has been an increase in small-scale extreme weather like tornadoes, hail, lightning, and dust storms.

Further, climate patterns generally describe phenomena over large areas such as continents and their major sub-regions.  It is very difficult to explain reliably the weather phenomena at the small scale from climate histories and patterns – making it all but impossible to correlate individual local events with climate change.

Even so, some – like the Center for American Progress – would like to convince people that the occurrence of seemingly extreme weather events is symptomatic or predictive of climate change.  However, extreme weather events always have some probability of occurring, along with the likelihood of occurring back to back.  If these events are indeed influenced by climate change, it may be that they have an increased chance of occurring.  But whether these events are happening more frequently is something we will only be able to know after observing a long period of time.

Simply having an extreme event, hot or cold, wet or dry, is not an indicator of the climate change currently being brokered to the American public as an unquestionable reality and a crisis. Some might find it satisfying to make statements relating weather events to climate change, because that condenses the complex issue of global climate dynamics into a small and personal experience. That is not science, and not an appropriate response to weather.