Burack: Understanding the Connection Between Weather, Climate

By Thomas Burack

It’s once again that time of year when many New Hampshire residents are welcoming the return of warmer weather and being outdoors enjoying all that New Hampshire has to offer. With the arrival of spring also comes the celebration of Earth Day, a time when many of us think about the things we can do to maintain and restore our environment. Addressing climate change is increasingly high on the list of people’s priorities. Climate change is real, serious, substantially man-made and a condition that affects us all. However, the severity of this past winter, due in part to the phenomenon referred to as the “Polar Vortex,” has raised a fundamental question – “how can it be so cold if the planet is supposed to be warming?” The answer can be found by distinguishing between weather and climate.  

A cold snap in the winter doesn’t mean that Earth’s overall temperature has stopped warming or that our climate has stopped changing. It simply means that the weather for this region, during this winter, has been cold. While New Hampshire experienced sub-zero temperatures, Alaska was in the 60s, parts of England were paralyzed by rainfall not seen in 250 years, California was experiencing a 500-year drought, and Australia was gripped by a heat wave that was killing wildlife. Weather is defined as the state of the atmosphere with respect to wind, temperature, cloudiness, humidity or precipitation at a given time and place. These conditions change from day to day or even from year to year. 

Climate, on the other hand, describes the average weather for a region over an extended period of years. The climate is determined by the long-term weather patterns over decades. Scientists measure it by calculating the 30-year averages for weather conditions. Residents in New Hampshire also have an intuitive sense of climate, expressed as our expectations for the weather. For example, we have wardrobes for each of the four seasons, we buy vehicles that can perform in all manner of road conditions and we know the best months to head to the beach or a lake to  beat the heat. Climate affects how we live, but it also affects natural systems. For instance, New Hampshire’s iconic forests are dependent on abundant rain to grow and cold temperatures to lock out southern species and pests. 

While the weather varies from day to day, on a year to year basis, the climate has historically been stable, a fact that has allowed natural systems to become established and human communities to adapt to their regions’ specific conditions. However, since the beginning of the industrial revolution, Earth’s temperature has warmed considerably as greenhouse gases have trapped a greater portion of the Sun’s energy. To understand how the climate in locations around the country and globe have changed, scientists have compared recent and long-term observations of the weather patterns.  

One pattern observed has been a warming in the Arctic to the north that has led to a decline in sea ice and increased snowmelt on land. Since ice and snow reflect sunlight back into space, both of them help to keep the Arctic cold. However, as they melt, they leave behind darker land and ocean water, which absorb sunlight and thereby cause increased warming in that region. An unexpected outcome of a warmer Arctic is a weaker jet stream, the high-level river of wind that circles the globe. Normally in winter, the jet stream tightly circles the Arctic, keeping the arctic air trapped to the North. But as the jet stream slows, it seems to allow frigid air to spill south and cause the severe conditions that we experienced this past winter.

Understanding the connection and distinction between weather and climate will help us all to understand how a single cold winter or cool summer doesn’t indicate that the climate has finally stopped changing or that overall temperatures on Earth have stopped rising.

The first Earth Day some forty-four years ago was a call to action to help protect and restore our environment. In a similar fashion, we should all view today’s Earth Day-and every day-as an opportunity to reduce our energy consumption to reduce the greenhouse gases that are causing climate change, and to become more prepared to deal with how climate change will impact our cities and towns, homes and businesses, and the environment all around us.

Thomas Burack is the commissioner of the NHDES.