Global warming and climate change refer to an increase in average global temperatures. Natural events and human activities are believed to be contributing to an increase in average global temperatures. This is caused primarily by increases in greenhouse gases such as Carbon Dioxide (CO2).
A warming planet thus leads to a change in climate which can affect weather in various ways, as discussed further below.
What are the main indicators of Climate Change?
What is the Greenhouse Effect?
The term greenhouse is used in conjunction with the phenomenon known as the greenhouse effect.
Energy from the sun drives the earth’s weather and climate, and heats the earth’s surface;
In turn, the earth radiates energy back into space;
Some atmospheric gases (water vapor, carbon dioxide, and other gases) trap some of the outgoing energy, retaining heat somewhat like the glass panels of a greenhouse;
These gases are therefore known as greenhouse gases;
The greenhouse effect is the rise in temperature on Earth as certain gases in the atmosphere trap energy.
Six main greenhouse gases are carbon dioxide (CO2), methane (CH4) (which is 20 times as potent a greenhouse gas as carbon dioxide) and nitrous oxide (N2O), plus three fluorinated industrial gases: hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulphur hexafluoride (SF6). Water vapor is also considered a greenhouse gas.
The Greenhouse effect is natural. What do we have to do with it?
Many of these greenhouse gases are actually life-enabling, for without them, heat would escape back into space and the Earth’s average temperature would be a lot colder.
However, if the greenhouse effect becomes stronger, then more heat gets trapped than needed, and the Earth might become less habitable for humans, plants and animals.
Carbon dioxide, though not the most potent of greenhouse gases, is the most significant one. Human activity has caused an imbalance in the natural cycle of the greenhouse effect and related processes. NASA’s Earth Observatory is worth quoting the effect human activity is having on the natural carbon cycle, for example:
Another way of looking at this is with a simple analogy: consider salt and human health:
A small amount of salt is essential for human life;
Slightly more salt in our diet often makes food tastier;
Too much salt can be harmful to our health.
In a similar way, greenhouse gases are essential for our planet; the planet may be able to deal with slightly increased levels of such gases, but too much will affect the health of the whole planet.
The other difference between the natural carbon cycle and human-induced climate change is that the latter is rapid. This means that ecosystems have less chance of adapting to the changes that will result and so the effects felt will be worse and more dramatic it things continue along the current trajectory.
The climate has always varied in the past. How is this any different?
In the 1880 – 1935 period, the temperature anomaly was consistently negative. In contrast, the since 1980 the anomaly has been consistently positive. The 1909 temperature anomaly (-0.47oC) was the lowest year on record. Since 1909, global temperature has warmed, with the most recent years showing the highest anomalies of +0.6 oC in the past 120 years.
A NASA’s GISS animation also shows how most parts of the world have experienced this warming, recently:
As well as the links above, see also Skeptical Science, which, while examining the arguments of global warming skepticism, provides information on causes of anthropogenic global warming.
Doesn’t recent record cold weather disprove Global Warming?
The confusion that sometimes arises is the difference between climate change and weather patterns. Weather patterns describe short term events, while climate change is a longer process that affects the weather. A warming planet is actually consistent with increasing cold, increasing rain and other extremes, as an overall warmer planet changes weather patterns everywhere at all times of the year.
To get an idea of how looking at short term changes only can lead to a conclusion that global warming has stopped, or doesn’t exist, see Alden Griffith’s has global warming stopped?
(As an aside, those crying foul of global warming claims when going through extremely cold weather in Europe for example in 2010, later found their summers to be full of heat waves. The point here is that a specific short period such as a cold winter — or even a hot summer — is not proof alone that global warming has stopped (or increased); short term variability can mask longer term trends.)