Featured Phenomenon: Changing Air Temperatures
Earth-orbiting satellites and other technological advances have enabled scientists to observe changing atmospheric temperatures as they collect many different types of information about our planet and its climate on a global scale. Studying climate data collected over many years reveal the signals of a changing climate. Scientific evidence supports an upward temperature trend across the entire Earth since the early 20th century – and most notably since the late 1970s. The planet's average surface temperature has risen about 2.0 degrees Fahrenheit (1.1 degrees Celsius) since the late 19th century, a change driven largely by increased carbon dioxide and other human-made emissions into the atmosphere. Most of the warming occurred in the past 35 years, with 16 of the 17 warmest years on record occurring since 2001 and the warmest year on record occurring in 2016. Not only was 2016 the warmest year on record, but eight of the 12 months that make up the year — from January through September, with the exception of June — were the warmest on record for those respective months.
The Earth's climate has changed throughout history. Just in the last 650,000 years, there have been seven cycles of glacial advance and retreat, with the abrupt end of the last ice age about 7,000 years ago marking the beginning of the modern climate era — and of human civilization. Most of these climate changes are attributed to very small variations in Earth’s orbit that change the amount of solar energy our planet receives. The current warming trend is of particular significance because most of it is very likely human-induced and proceeding at a rate that is unprecedented in the past 1,300 years.
Two terms that are often incorrectly used interchangeably are “global warming” and “climate change.” Global warming is the observed upward global temperature trend since the early 20th century, mainly due to the increase in emissions from burning fossil fuels. Climate change is a broader term that describes all changes in different Earth spheres, not just temperature changes, connected to the increase in emissions.
Weather and climate are two other terms that are frequently confused in the discussion of climate change. Both refer to events with broadly different spatial and time scales. Weather refers to atmospheric conditions that occur locally over short periods of time – from minutes to hours or days. Familiar examples include rain, snow, clouds, winds, floods or thunderstorms. Remember, weather is local and short-term. Climate, on the other hand, refers to the long-term regional or global average of temperature, humidity and rainfall patterns over seasons, years or decades. Climate is regional or global and long-term. Erratic weather in your neighborhood – whether rain or drought – may or may not be a symptom of global climate change. To know, we must monitor weather patterns over many years.
Credit: NASA Climate