You vacation based on climate, but you pack based on weather

While 2014 was reported as the warmest year on record globally, the Great Lakes region experienced one of the coldest winters on record last year. What gives? The answer lies in the difference between weather and climate.

Photo: Land and Ocean Temperature Percentiles, NOAA
Photo: Land and Ocean Temperature Percentiles, NOAA

In early January, the National Oceanic and Atmospheric Administration (NOAA) reported that 2014 was the warmest year on record, with an annually-averaged temperature across global land and ocean surfaces 0.69 degrees Celsius (1.24 degrees Fahrenheit) above the 20th century average of 13.9 C (57.0 F). If living in the Midwest, this datum might seem strange given the colder-than-average winter last year. The difference can be explained by contrasting weather from climate.

While both terms refer to environmental variables or conditions such as temperature or humidity, weather amounts to short-term variations in these conditions of the atmosphere that we experience on a day-to-day, week-to-week, or month-to-month basis. The weather in the upper Midwest was record cold with above-average precipitation in many locations last year. On the other hand, climate is the average of daily weather conditions for an extended period of time, over a period of years, decades or centuries. NOAA differentiates the two this way (courtesy of Mark Twain): Climate is what you expect, weather is what you get.

Both weather and climate can be studied and tracked locally. Put differently, the difference between the two is in the scale of time, not the physical scale of local vs. global. Consider NOAA’s graphic showing land and ocean temperature percentiles for 2014. We see that the Midwest U.S. is blue, and if you experienced last winter here, the color alone makes you shiver! However, looking at the legend we see this is not a graphic showing temperature extremes or anomalies, it is showing annual average temperature relative to the long-term average for individual locations across the globe. Essentially, this graphic is showing the difference between weather and climate for 2014 (excluding precipitation, of course).

Visualizing the data in this way, it is easier to grasp that weather across the planet as a whole was warmer in 2014 than the climate expected based on historic conditions over more than a century.

Another take-away is that, like changing weather, climate change is experienced locally (regionally) in different ways. To borrow from the real estate world, climate change impact is all about location, location, location. To better understand these regional differences and more appropriately prepare for regional climate changes, NOAA established a national network of Regional Integrated Sciences and Assessments (RISAs) that focus on adaptation to climate change and variability. For the Great Lakes region, the Great Lakes Integrated Sciences and Assessments (GLISA) is the NOAA RISA.

The GLISA website includes compilations and summaries of scientific research from government organizations and major universities. One such resource is a fact sheet detailing Climate Change in the Great Lakes Region. We see that across the region, since 1900, annual average temperatures have increased by 2.0 F (1.1 C) and that by 2050, average air temperatures are projected to increase by an additional 1.8 to 5.4 F (1 to 3 C). These data are a combination of climatic observations and projections. What the weather will be next year is anyone’s guess, but the long-term climate trend in the Great Lakes region is warmer (and generally wetter). Remember, you vacation based on climate, but you pack based on weather!

For more information on climate trends and predictions for the Great Lakes region, explore the GLISA website in more depth, or contact a member of the Michigan State University Extension Climate Outreach Team.

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