Causes and Effects of Global Warming
Lesson
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 become more common as temperatures increase.
Causes of Global Warming
Although there have been ups and downs over time, the average global temperature has been rising since the end of the Pleistocene. 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 which release greenhouse gases into the atmosphere. Greenhouse gases, such as carbon dioxide, keep the atmosphere warm When humans burn fossil fuels for energy, 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 greater greenhouse effect. The result is increased global warming. Pictured below is the increase in carbon dioxide since 1960 (Figure below).
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
Many effects of global warming have already been observed. As Earth has gotten warmer, glaciers and sea ice have melted. This has raised the level of water in the oceans by about 3 mm per year. Although this doesn’t sound like much, added together over the years it can be a lot: global sea level in 2021 was about 21-24 cm higher than it was in 1880. The rate of sea level rise is now accelerating, and scientific models predict that sea level is likely to rise an additional 30 cm by 2100. Storm surges from more frequent hurricanes, combined with higher sea levels, means that many coastal communities will face danger from flooding in the coming decades.
The extent of Arctic sea ice in summer has been decreasing rapidly. The ice pictured below is the sea ice minimum in 2016 (Figure below). The yellow line is the median minimum ice extent for 1981–2010.
Other effects of global warming include more extreme weather. Earth now has more frequent and severe storms, floods, heat waves, 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 to where temperatures are cooler, often to higher latitudes or higher altitudes. Those that already live in cold climates are losing habitat. The timing of migration and egg-laying behaviors in birds is shifting. There are many more examples of the effects of changing climate.
Summary
- Greenhouse gases trap heat in the atmosphere. Burning fossil fuels and other human activities release greenhouse gases into the atmosphere.
- Greenhouse gas levels in the atmosphere are increasing. Global temperatures are increasing.
- Changes due to increasing temperatures are seen around the globe. Living organisms and humans are also affected.
Review
- What do you expect to happen if you increase the amount of greenhouse gases in the atmosphere?
- What has happened to the level of carbon dioxide in the atmosphere in the past several decades (use numbers and units)?
- What has happened to sea level since 1870 (use numbers and units)?
- What are some of the effects of climate change that are already being seen?
Asked by Students
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