Global Warming Facts
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1/ What is global warming?

Global warming is when the planet becomes warmer than it “should” be. It is such a big concern at the moment because it seems that temperatures around the world are rising at a faster rate than ever before. Over the past 150 years, humans have changed the way they live and the way they use the earth. It is thought that these human activities are causing the temperature to rise.

Mean temperatures over the whole planet have risen by about 0.74° C (1.33° F) in the last 100 years. More than half of this increase has happened in the last 25 years. Scientists use many temperature records to work out the average temperatures from around the world. They take evidence from thousands of observation sites both on land and sea. They represent a large portion of the Earth’s surface. Scientists make sure their calculations are correct by always checking their information from the different weather stations. They also check their equipment so that their measurements are accurate.

The temperature changes are happening too quickly and the planet cannot cope. This is a worry because the planet can only cope with changes in temperature which happen over periods of tens and hundreds of thousands of years and certainly over millions of years. This gives the planet time to get used to the changes and causes less stress to the planet and the humans. That’s the natural way for temperature changes to occur.

The current rate of change is much, much faster than any changes have ever happened before as far as we are aware. This is a real problem because animals and plants can adapt to slow changes such as migration, but a rapid change will eventually lead to large extinctions of many species. The human population of the earth is also dependent on a stable climate for established agriculture and also cities. Millions if not billions of people will suffer from the consequences of global warming and especially people in the undeveloped nations who are the most vulnerable of all (ref).

Climate changes in the past over Geological time periods (millions and tens of millions of years) have been very drastic. During cold periods, much of the planet, even thousands of miles from both poles have been ice-covered by huge glaciers and during warm periods. These regions may have been sub-tropical or even tropical. As well as this there have been large changes in sea-level so that some areas of land have either become flooded completely or left high and dry.

It is potentially an enormous problem if the global temperature rises to a level where it is affecting the Antarctic ice-caps. They may begin to melt and cause sea-level rises which can be globally measured in meters. There are many cities around the world that are on the coast and they would be flooded and probably have to be abandoned. There are also many countries, especially poorer countries where a large part of the population live in coastal regions. In this case the farm-land would be flooded and the people will be left homeless. They will not have the ability to feed themselves. In some cases entire island nations (even though they are small) in the Pacific Ocean could simply disappear.

There are two questions about Global Warming that the world has at the moment and neither of them has a clear answer. There is much scientific debate and an awful lot of political argument too.

1/ If Global Warming is the result of man's activities:

Can we stop it?

How do we stop it?

Whose responsibility is it to stop it?

2/ As Global Warming is taking place, regardless of the cause:

How do we deal with it's effects?

2/ How do we know that global warming has taken place?

We know that global warming has taken place because millions of temperature measurements have been taken over many decades from all points on the earth. The measurement of global warming is of a wide variety of statistics over a period of time and therefore can be quite complex to explain and understand.

The global average air temperature shows a linear trend of 0.74 [0.56 to 0.92] °C
for the 100-years from 1906-2005

This sounds like a small increase and is easily misinterpreted

For example some would say that when 2006 is described as being "the hottest in Britain since 1659" (when temperatures began to be recorded in central England) it simply means that it was as warm in 2006 as it was in 1659 and there wasn't any worry about global warming then, so why is there now?

	Hottest since 1659 means that was when temperatures started to be recorded - not that 1659 was the 2nd hottest year ever.
	Past record years have come pretty much at random and certainly not in groups. The fourth hottest year in Britain since 1659 was 1949, 8 of the 10 hottest years since 1860 have all occurred in the last decade.
	Daily variations in temperature can commonly be from 5°C to 10°C which makes the average 0.74°C rise difficult to spot by the individual in the shorter term.
	Some parts of the world are showing the effects of warming more than others. The Northern hemisphere for instance appears to be warming more than the Southern hemisphere, possibly because there is more land in the north and more sea in the south

Northern hemisphere average annual temperatures compared to the 1961-1990 average

3/ How does global warming affect our lives now?

It is difficult to say specifically what the current effects of global warming are as the weather over much of the globe is subject to large natural variations.

We cannot say categorically that a particular storm or event such as hurricane, tornado, flood etc. is a result of global warming as these things have always happened and there have always historically been years when there have been more of them than the average.

These are some of the effects that have been observed in recent years:

	Significantly increased precipitation in eastern parts of North and South America, northern Europe and northern and central Asia. » Greater prevalence of floods.
	Studies suggest that the ranges of plant and animal species are shifting towards the poles at around six kilometres a decade.
	The frequency of heavy precipitation events has increased over most land areas - consistent with warming and increases of atmospheric water vapour. » Greater prevalence of floods.
	Drying in the Sahel, the Mediterranean, southern Africa and parts of southern Asia. » Crop failures and increased regional conflict.
	More intense and longer droughts observed since the 1970s, particularly in the tropics and subtropics. » Crop failures.
	Annual average Arctic sea ice extent shrunk by 2.7 % per decade, decreases in summer 7.4 % » Effects on wildlife, particularly polar bears.
	Melting permafrost. Temperatures at the top of permafrost layer have generally increased since the 1980s by up to 3°C » Buildings and roads subside and ecosystems are altered across the arctic from Alaska to Canada and Russia.
	Cold days, cold nights and frost less frequent.
	Hot days, hot nights, and heat waves more frequent.
	Observational evidence for an increase of intense tropical cyclone activity in the North Atlantic since about 1970, correlated with increases of tropical sea surface temperatures.

Glacier retreat since 1960

These aspects of climate have not been observed to change so far:

Increased incidence of Tornadoes

Increased incidence of Dust-storms

Increased incidence of Hail

Increased incidence of Lightning

Melting Antarctic sea ice

4/ How will global warming affect our future?

The predicted effects of global warming will mean that more of what would have been "normal" storms become more destructive, heavy rainfall becomes very heavy rainfall, short droughts become longer droughts etc.

More extreme weather events will become more common

The worst potential effects of global warming are probably a result of melting of icecaps so causing global sea-levels to rise and flood many low-lying areas of the world including major cities and agricultural areas. The extent to which this might happen is dependent on how much the temperature may rise and this is the most difficult to forecast.

One of the currently most regarded estimates for this future warming is 1.8°C - this is in addition to warming that has already happened. IPCC There is however the possibility that this could be anywhere from a possible 1.1°C to as high as 6.4°C.

This warming effect is expected to be greater in the Northern than the Southern hemisphere and to become more pronounced at higher northern latitudes.

These are some of the predicted effects for the future.

	Snow cover is projected to contract.
	Widespread increases in thaw depth most permafrost regions.
	Sea ice is projected to shrink in both the Arctic and Antarctic.
	In some projections, Arctic late-summer sea ice disappears almost entirely by the latter part of the 21st century.
	Very likely that hot extremes, heat waves, and heavy precipitation events will continue to become more frequent.
	Likely that future tropical cyclones will become more intense, with larger peak wind speeds and more heavy precipitation.
	Anthropogenic warming and sea level rise would continue for centuries due to the timescales associated with climate processes and feedbacks, even if greenhouse gas concentrations were to be stabilized.
	Temperatures in excess of 1.9 to 4.6°C warmer than pre-industrial sustained for millennia…eventual melt of the Greenland ice sheet. Would raise sea level by 7m. Comparable to 125,000 years ago.

5/ How can we help reduce the effects of global warming?

It's about cutting power use and consumption generally - not so simple in a world where consumption is often admired and sometimes envied and where power use can make life more convenient or more interesting.

As a rule of thumb though anything you can do to use less energy and buy locally produced items of quality rather than cheap and cheerful in quantity will help. There are many guides as to what to do, some very effective, others less so, the most effective are:

	Fly less or not at all.
	Get a less polluting car and use it less often.
	Get more efficient refrigeration - fridges and freezers are on 24/7/365 and as a result use the most energy of any domestic appliance.
	Reduce the amount of heating your house or office needs, use insulation, stop draughts, turn the thermostat down 1 degree.
	Reduce water heating requirements, takes showers not baths, take normal showers, not power-showers, get a more efficient washing machine.
	Get low energy light bulbs and turn them off when not needed.

More details here

6/ How does global warming lead to worse storms?

The earth's weather is the result of the effect of heat energy coming from the sun combined with the atmosphere and oceans and the fact that the earth is rotating about its axis and around the sun.

Different parts of the earth heat up and cool down at different times of the day and year depending on incoming radiation, this causes air and water to move as winds and currents. In other words, the energy from the sun stirs up the earths atmosphere and oceans and causes what we call "weather".

The greater the amount of heat that arrives or gets kept behind means that the weather becomes more energetic. Global warming means more energy is retained by the earth to power the weather, so we are likely to get more frequent and more extreme weather conditions as various kinds of storms as this energy dissipates within the atmosphere.