Sun’s energy trapped by water vapour and gases in the atmosphere. It is a natural process but recently (100+ years) there's an:
Enhanced greenhouse effect
Earth is being heated up by the thickening ‘blanket’ of greenhouse gases including carbon compounds from burning forests and fossil fuel sources, plus livestock gut methane gas emissions and agricultural nitrous oxide, plus extra water vapour in highest- altitude clouds (from jet aircraft).
Most scientists believe that extra greenhouse gas emissions from human activity are large contributors to global climate change. Global concern in the 1990s led to the Kyoto Protocol that committed developed countries such as NZ, Japan and the EU to reduce their greenhouse gas output. There has been resistance to ratifying the Protocol by the USA and Australia
Kyoto Protocol - as a signatory, NZ’s target is to reduce greenhouse gas emissions to 1990 levels, by 2012 (currently our emissions are more than 5% above 1990 levels) by:
reducing emissions of greenhouse gases.
growing forests (which absorb CO2 from the atmosphere) to offset emissions.
helping other countries to reduce emissions.
The New Zealand Government has released a policy package that will assist us to achieve our target. This can be found on www.climatechange.govt.nz
Burning the fossil carbon storereleases CO2 gas. Fossil fuels are a limited ‘resource’ that is being burnt millions of times faster than the rate at which carbon was originally stored, from sunshine, by nature.
Electricity generationby burning coal or gas releases CO2. In contrast, electricity generated from hydro lake storage, wind generators or geothermal steam, does not release CO2.
Burning wood also releases CO2 but because trees absorb CO2 from the atmosphere to grow, the total impact of burning wood is neutral on carbon balance.
Measurements show that theconcentration of CO2 in the atmosphere is now higher than at any time during at least the past 420,000 years, if not several million years. It's grown beyond natural variation.
Living on a greenhouse planet
There is increasing evidence that the Earth is already warming up, leading to:
shrinking glaciers and sea ice.
changes to flowering times of plants.
changes to migration patterns of birds.
greater variability in weather, which may have major agricultural impacts such as floods and droughts.
a rise in sea levels which can threaten coastal areas (often densely populated).
For NZ, global warming could mean:
a rise in average sea level by perhaps 10cm by 2030 and 40cm by 2100.
up to twice the frequency of heavy rain and associated floods (especially in the west).
more droughts on east coasts of NZ and a one degree rise in average temperatures by 2030.
snow lines and glaciers will retreat. Some ski fields close.
the temperature change will begin altering the growing regions of crops and distribution of pest insects.
we would have more uncomfortably-hot summer days in cities, too, especially in Auckland and Christchurch.
Now that climate change has started, it is very hard to stop. Our past and present emissions of greenhouse gases have already committed the Earth to a substantial warming that will continue for the rest of the 21st century, and sea-level rises will continue for several more centuries.
