How many people do not believe in global warming just because of freezing temperatures in the summer? How often do you hear that global warming is a good thing because we would need or prefer warmer temperatures? Well, those people do not fully comprehend the difference between weather and climate. In case you cannot convince your opponent, check my blog entry It is really happening.

 

Weather is not climate

Unlike climate, weather does refer to short-term variations in the atmosphere (Glossary of Meteorology). Thus, weather refers to the minute-to-minute, day-to-day or month-to-month temperature, to precipitation and wind, etc. Instead, climate reflects the atmospheric behaviour (temperature, precipitation, wind, etc.) over a longer period of time (NASA) and may be seen as the average of weather over time and space or simply as the statistics of weather. Therefore, we are only able to talk about climate considering relatively long time spans.

 

 

 Climate Change

When talking about global warming, the difference between weather and climate is of particular importance. Climate change refers to a long-term change in the average weather conditions, and may be seen as a natural process. This process is accompanied by short-term climate variations like El Niño, La Niña, volcanic eruptions or other repeating changes to the climate system (NASA).

 

Human-caused global warming

In the past century, the earth’s average surface temperature has rapidly increased (IPCC). This fast warming of the climate system has to be traced back to human activities, mainly to emissions of CO2 (mainly traffic, electricity and heating) and methan (mainly cattle farming). As observable in the bar chart, the natural range of climate fluctuations of +/- 0.5 degrees has already been surpassed.

 

Temperature Increase of the Last Century

 

White Christmas?

What does this mean for Christmas? Do your parents always tell you of massive snowfalls when they were young? Can’t we get snow for Christmas anymore? Well, we can. The average temperature is clearly rising, but with increasing temperatures climate variability does also increase. In other words, extreme events are more likely to occur (you’ll read a blog post about this relation next week). In this sense, we may get snow for Christmas in the future, but most likely with a very low frequency of occurrence.

 

 

Graphic Source:

GISTEMP Team, 2016: GISS Surface Temperature Analysis (GISTEMP). NASA Goddard Institute for Space Studies. Dataset accessed 2016-12-23 at http://data.giss.nasa.gov/gistemp/.