The figure shows the combined land-surface air and sea surface temperatures (degrees Centigrade) 1861 to 1998, relative to the average temperature between 1961 and 1990. The mean global surface temperature has increased by about 0.3 to 0.6°C since the late 19th century and by about 0.2 to 0.3°C over the last 40 years, which is the period with most reliable data. Recent years have been among the warmest since 1860 - the period for which instrumen...

Using the IS92 emission scenarios, projected global mean temperature changes relative to 1990 were calculated up to 2100. Climate models calculate that the global mean surface temperature could rise by about 1 to 4.5 centigrade by 2100. The topmost curve is for IS92e, assuming constant aerosol concentrations beyond 1990 and high climate sensitivity of 4.5 °C. The lowest curve is for IS92c and assumes constant aerosol concentrations beyond 1990 an...

Using the IS92 emission scenarios, projected global mean sea level increases relative to 1990 were calculated up to 2100. Taking into account the ranges in the estimate of climate sensitivity and ice melt parameters, and the full set of IS92 emission scenarios, the models project an increase in global mean sea level of between 13 and 94 cm. During the fist half of the next century, the choice of emission scenario has relatively little effect on ...

Over the last 100 years, the global sea level has risen by about 10 to 25 cm. Sea level change is difficult to measure. Relative sea level changes have been derived mainly from tide-gauge data. In the conventional tide-gauge system, the sea level is measured relative to a land-based tide-gauge benchmark. The major problem is that the land experiences vertical movements (e.g. from isostatic effects, neotectonism, and sedimentation), and these get ...

The figure shows a comparison of current vegetation zones at a hypothetical dry temperate mountain site with simulated vegetation zones under a climate-warming scenario. Mountains cover about 20% of the Earth's continents and serve as an important water source for most major rivers. Paleologic records indicate that climate warming in the past has caused vegetation zones to shift to higher elevations, resulting in the loss of some species and ecos...

This map depicts the unequal distribution of industry in the world. The significant part of carbon dioxide emissions comes from energy production, industrial processes and transport. The industrialised countries consequently must bear the main responsibility of reducing emissions of carbon dioxide.

The table lists some of the main greenhouse gases (such as carbon dioxide, methane, and freons) and their concentrations in pre-industrial times and in 1994; atmospheric lifetimes; anthropogenic sources; and Global Warming Potential. Greenhouse gases are a key factor in global warming, as they trap the radiating heat in the atmosphere, reflecting it back to the atmosphere.

CO2 concentrations in the atmosphere have been measured at an altitude of about 4,000 meters on the peak of Mauna Loa mountain in Hawaii since 1958. The measurements at this location, remote from local sources of pollution, have clearly shown that atmospheric concentrations of CO2 are increasing. The mean concentration of approximately 316 parts per million by volume (ppmv) in 1958 rose to approximately 369 ppmv in 1998. The annual variation is d...

The global carbon cycle shows the carbon reservoirs in GtC (gigatonne= one thousand million tonnes) and fluxes in GtC/year. The indicated figures are annual averages over the period 1980 to 1989. The component cycles are simplified and the figures present average values. The riverine flux, particularly the anthropogenic portion, is currently very poorly quantified and is not shown here. Evidence is accumulating that many of the fluxes can fluct...

The figure shows change in cereals production under three different GCM equilibrium scenarios (percent from base estimated in 2060). While there are still uncertainties about whether climate change will cause global agricultural production to increase or decrease, changes in the aggregate level of production are expected to be small or moderate. The result of the studies that have been conducted so far vary depending on such variables as the trad...

The global conveyor belt thermohaline circulation is driven primarily by the formation and sinking of deep water (from around 1500m to the Antarctic bottom water overlying the bottom of the ocean) in the Norwegian Sea. When the strength of the haline forcing increases due to excess precipitation, runoff, or ice melt the conveyor belt will weaken or even shut down. The variability in the strength of the conveyor belt will lead to climate change in...

Projected anthropogenic CO2 emissions from fossil fuel use, deforestation and cement production are shown for some of the IPCC emission scenarios. The highest emission scenario - IS92e - assumes moderate population growth, high economic growth, high fossil fuel availability, and a phase out of nuclear power; and the lowest emission scenario - IS92c - assumes low population growth, low economic growth, and severe constraints on fossil fuel suppli...

If greenhouse gas concentrations keep rising, climatic changes are likely to result. Those changes will potentially have wide-ranging effects on the environment and socio-economic and related sectors, such as health, agriculture, forests, water resources, coastal areas and biodiversity.

Rising sea level would destroy weak parts of the sand belt, which is essential for the protection of lagoons and the low-lying reclaimed lands in the Nile delta of Egypt (Mediterranean Sea). The impacts would be very serious: One third of Egypt's fish catches are made in the lagoons. Sea level rise would change the water quality and affect most fresh water fish. Valuable agricultural land would be inundated.

In 1988, UNEP and WMO jointly established the Intergovernmental Panel on Climate Change (IPCC) as concern over changes in the climate became a political issue. The purpose of the IPCC was to assess the state of knowledge on the various aspects of climate change including science, environmental and socio-economic impacts and response strategies. The IPCC is recognized as the most authoritative scientific and technical voice on these issues, and it...

Human activities are causing greenhouse gas levels in the atmosphere to increase. This graphic explains how solar energy is absorbed by the earth's surface, causing the earth to warm and to emit infrared radiation. The greenhouse gases then trap the infrared radiation, thus warming the atmosphere.

One study suggests that although global water conditions may worsen by 2025 due to population pressure, climate change could have a net positive impact on global water resources. NB! Note that other studies indicate that with present consumption patterns, 2 of every 3 persons on Earth will experience water stress by 2025. The diagram on the left side shows the result of this particular study, indicating the water availability for the population...

Over the last 400,000 years the Earth's climate has been unstable, with very significant temperature changes, going from a warm climate to an ice age in as rapidly as a few decades. These rapid changes suggest that climate may be quite sensitive to internal or external climate forcings and feedbacks. This figures have been derived from the Vostok ice core, taken in Antarctica.

Developing countries, whose economies often rely heavily on one or two agricultural products, are especially vulnerable to climate change. This graphic shows that with an increase of only 2 degrees Celsius, there would be a dramatic decrease in the amount of land suitable for growing Robusta coffee in Uganda.

The icebreaking date for the Tornio River in Finland has been recorded since 1693. With the increased greenhouse effect, impacts on the cryosphere are likely. One impact will be less ice on rivers and lakes. Freeze-up dates will be delayed, and break-up will begin earlier. The period of river-ice could be shortened by up to a month. Many rivers within the temperate regions could become ice-free or develop only intermittent or partial ice coverage...