Whether weather or climate change?

A common misunderstanding is the distinction between weather and climate. Where weather is measured on day-to-day or yearly time scales, climate is measured in decades, centuries and millennia. Climate can be thought of as weather averaged over many, many years. Climate is critically important when determining trends and patterns, anomalies and outliers; whereas, weather is important for day-to-day living.

Therefore, a common mistake would be to make claims like, “Thank you global warming for this beautiful weather,” or “Snow in May? Global warming must not be happening.”

Global warming, commonly associated with terms such as “climate change,” “climate destabilization,” or “global climate change,” is the change of the natural variation in our weather systems over time, including the increase in average temperatures around the globe. Meaning, our climate will reflect the long-term trend of weather variation.

So, what has our recent weather look like over longer time scales? Here’s a start…

(Data source: NASA Goddard Institute for Space Studies. Visualization credit: NASA Goddard Space Flight Center Scientific Visualization Studio)

This clip visualizes temperature data from 1881 to 2007 where reds indicate temperatures higher than the average temperatures (baseline period of 1951-1980), and blues indicate lower than average temperatures. The year 1881 is typically used as the beginning of the modern era of weather data collection at weather stations around the world.

According to NASA:

• 2011 was the 9^th warmest year in instrumental record (since 1880).
• 9 of the 10 warmest years have occurred since 2000, the other being 1998.

According to National Climatic Data Center:

• Compared to the previous La Nina years, 2011 was the warmest observed.
• 2011 was the 35^th consecutive year that the global temperature was above average (the last year was 1976).
• 2011 was the 2^nd wettest year on record (behind 2010) with globally-averaged precipitation over land.

James Hansen, a climate scientist at NASA’s Goddard Institute for Space Studies, further explains the relationship between climate change and increased weather variation in a short interview with the New York Times.