APCC - Climate Change (Lesson)
Climate Change
What's the weather like?
If someone across the country asks you what the weather is like today, you need to consider several factors. Air temperature, humidity, wind speed, the amount and types of clouds, and precipitation are all part of a thorough weather report.
What is the Weather?
Weather takes place in the atmosphere, virtually all of it in the lower atmosphere. Weather describes what the atmosphere is like at a specific time and place. A location's weather depends on:
- air temperature
- air pressure
- fog
- humidity
- cloud cover
- precipitation
- wind speed and direction
All of these characteristics are directly related to the amount of energy that is in the system and where that energy is. The ultimate source of this energy is the Sun.
Weather is the change we experience from day to day. Weather can change rapidly.
What is Climate?
Although almost anything can happen with the weather, the climate is more predictable. The weather on a particular winter day in San Diego may be colder than on the same day in Lake Tahoe, but, on average, Tahoe's winter climate is significantly colder than San Diego's.
Winter weather at Lake Tahoe doesn't much resemble winter weather in San Diego even though they're both in California.
Climate is the long-term average of weather in a particular spot. A good climate is why we choose to vacation in Hawaii in February, even though the weather is not guaranteed to be good! A location's climate can be described by its air temperature, humidity, wind speed and direction, and the type, quantity, and frequency of precipitation.
The climate for a particular place is steady and changes only very slowly. Climate is determined by many factors, including the angle of the Sun, the likelihood of cloud cover, and air pressure. All of these factors are related to the amount of energy that is found in that location over time.
What is the human cost of warmer temperatures?
Many lands are marginal for farming. When rainfall is normal or high, the lands can produce. When rainfall is low, no crops grow. Drought makes marginal lands unsuitable for farming. Drought can also make good lands more difficult to farm. These changes will increase as temperatures warm.
Causes of Global Warming
The average global temperature has been rising since the end of the Pleistocene, with some ups and downs, of course. Rising temperatures are natural for this time period. But natural causes cannot explain all the warming that's been happening. There is some other factor at work.
Recent global warming is due mainly to human actions. The actions involve releasing greenhouse gases into the atmosphere. Remember that greenhouse gases keep the atmosphere warm? And that carbon dioxide is a greenhouse gas? When you burn fossil fuels, carbon dioxide is released into the atmosphere. The more carbon dioxide in the atmosphere, the better the atmosphere can trap heat. In other words, an increase in greenhouse gases leads to a greater greenhouse effect. The result is increased global warming. Pictured in this graph below is the increase in carbon dioxide since 1960.
How much more carbon dioxide was in the air in 2010 than in 1960?
Burning forests also releases carbon dioxide into the atmosphere. Other human activities release greenhouse gases into the atmosphere. For example, growing rice and raising livestock both produce methane.
Effects of Global Warming
There are already many effects of global warming being seen. As Earth has gotten warmer, sea ice has melted. This has raised the level of water in the oceans (see graph below).
The overall trend in sea level since 1870 - it has risen about 9 inches.
Be sure to watch the following video on climate change from NASA.
The extent of Arctic sea ice in summer has been decreasing rapidly. The ice pictured below is the sea ice minimum in 2011 (see image below). The yellow line is the median minimum ice extent for 1979-2000.
The sea ice minimum for 2011 was the second-lowest on record.
Other effects of global warming include more extreme weather. Earth now has more severe storms, floods, heatwaves, and droughts than it did just a few decades ago. Many living things cannot adjust to the changing climate. Coral reefs in many parts of the world are struggling to survive. Species are moving uphill where temperatures are cooler. Those at the top of the mountain are being runoff. Migration and egg-laying behaviors in birds are off of their normal. There are many more examples of the effects of changing climate.
Increasing Temperatures
While temperatures have risen since the end of the Pleistocene, 10,000 years ago, this rate of increase has been more rapid in the past century and has risen even faster since 1990. The 12 warmest years on record have all occurred since 2001, and the 20 warmest years have occurred since 1987 through 2011. (see graph below). The 2000s were the warmest decade yet.
Recent temperature increases show how much temperature has risen since the Industrial Revolution began. Annual variations aside, the average global temperature increased at an average rate of 0.17°F per decade since 1901. Worldwide, 2011–2020 was the warmest decade on record since thermometer-based observations began (EPA).
Which year has been the warmest on record?
Greenhouse Gas Emissions
The United States has long been the largest emitter of greenhouse gases, with about 20% of total emissions in 2004. As a result of China's rapid economic growth, its emissions surpassed those of the United States in 2008. However, it's also important to keep in mind that the United States has only about one-fifth the population of China. What's the significance of this? The average United States citizen produces far more greenhouse gas emissions than the average Chinese person.
Do polar bears belong in garbage dumps?
Changes due to warmer temperatures are becoming more visible. The Arctic is covered with ice less of the year, so polar bears can't hunt and are raiding garbage dumps for food. Extreme weather events are becoming more common as the weather becomes stranger. The sea level is rising, which is a problem during storms.
Global Warming
With more greenhouse gases trapping heat, average annual global temperatures are rising. This is known as global warming. Be sure to watch Global warming - How Humans are Affecting our Planet Links to an external site. from NASA. This video discusses the basics of global warming science.
Changes Due to Warming Temperatures
The following images show changes in the Earth and organisms as a result of global warming.
(a) Breakup of the Larsen Ice Shelf in Antarctica in 2002 was related to climate warming in the region. (b) The Boulder Glacier has melted back tremendously since 1985. Other mountain glaciers around the world are also melting.
Permafrost is melting and its extent decreasing. There are now fewer summer lakes in Siberia.
The timing of events for species is changing. Mating and migrations take place earlier in the spring months. Species that can are moving their ranges uphill. Some regions that were already marginal for agriculture are no longer arable because they have become too warm or dry.
RESOURCES IN THIS MODULE ARE OPEN EDUCATIONAL RESOURCES (OER) OR CREATED BY GAVS UNLESS OTHERWISE NOTED. SOME IMAGES USED UNDER SUBSCRIPTION.