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Carbon dioxide in the atmosphere matters

Science proves that the Global Warming effect is caused by the concentration of greenhouse gases in the atmosphere. But what is a greenhouse gas and how does it warm the earth?

We know that a certain concentration of greenhouse gases in the atmosphere is necessary for life as we know it. As Dr Phil McFadden explains, "the planet surface is about 33°C warmer than it would be without the greenhouse effect". So we need some greenhouse gases in the atmosphere to make human life comfortable. However the converse is also true, to great a concentration of greenhouse gases in the atmosphere will warm the planet beyond the comfort zone for humans.

Over the last 200 years mankind has significantly added to the concentration of greenhouse gases in the atmosphere.

The reason a greenhouse gas warms the planet is the number of atoms. The 3-Atoms in Carbon Dioxide trap and emit the suns infrared energy, causing global warming. Read more of the science.

There six greenhouse gases covered by the Kyoto Protocol and included in the GHG Protocol Corporate Standard are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulphur hexafluoride (SF6).

The atomic structure of these gases means they have different powers of trapping and emitting energy. The Global Warming Potential is the scale by which the greenhouse gases warming effect is measured. The measurement compares the warming effect to carbon dioxide. Table 1 shows Methane has 25 times more warming potential than carbon dioxide and lasts 12 years in the atmosphere.

Table 1 - Global Warming Potential

Greenhouse Gas	Lifetime (years)	GWP In 100 years
Carbon Dioxide	See below^a	1
Methane	12	25
Nitrous Oxide	114	298
HFC-23 (Hydrofluorocarbon)	270	14,800
PFC-14 (Perfluorocarbon)	50,000	7,390
Sulfur Hexafluoride	3,200	22,800

Source: Direct Global Warming Potentials, Table 2.14, page 212, 2007 IPCC AR4

Notes:
^a "About 50% of a CO2 increase will be removed from the atmosphere within 30 years, and a further 30% will be removed within a few centuries. The remaining 20% may stay in the atmosphere for many thousands of years.", IPCC - Climate Change 2007: Working Group 1: The Physical Science Basis

The message from science is clear - we urgently need to act now to reduce global carbon emissions and help stop damaging climate change.

The evidence linking human carbon emissions to global warming is clear. We need to make deep cuts in carbon emissions in order to avoid the irreversible consequences of damaging climate change.

Those consequences become severe once temperatures have risen above 2 degrees Celsius. We must and can avoid this much warming.