Recent and Long Term Changes in Climate

• To advance scientific knownledge about climate change caused by human activities examines all the relevant scienfic litrature • Including natural, economic and social impacts and risks • Contains projected changes in temperature, precipitation, droughts, sea levels, arctic sea ice etc

Average weather conditions in a particular area, over a particular time period (temperture, precipitation, radiation, wind speed, humidity - long time scale)

Atmospheric conditions in a particular area, over a particular time (temperature, precipitation, radiation, wind speed, humidity - shorter time scale)

Changes in average weather in a particular area, over time

Needs to be long enough to be a sensible average, and short enough to be relevant to animals (including humans) and plants

• The balance between incoming energy from the Sun (shortwave) and outgoing energy from the Earth (longwave)

It causes the climate to change

The effect of a process of Earth’s energy balance, relative to 1750 pre-industrial baseline It’s a globally average value expressed in W/m²

• Changes in insolation caused by changes in the Earth’s orbit/axis (10-100ka cycles) • Called the Milankovitch cycles (change ±20%)

• Sunspots caused by changes in the magnetic pressure on the surface of the sun in association with decreases in the surrounding atmospheric pressure • 11-yr cycles • The warmer area around the sport gives out increased radiation, hence warming

• Darker forest vs lighter crop lands (due to deforestation) • Resulted in colour of the surface to change • Hence more light would be refleced on the lighter side, leading to a cooling effect

The black within the glacier is due to soot, which has been depoitted into the glacier Results in increased absorption due to darker colour (warming effect)

CO₂, CH₄, N₂O

Aerosols can scatter/absorb solar radiation AND act as cloud condensation nuclei: more clouds for longer period

• Dust • Sea Salt • Sulphate from volcanoes

• Biomass burning • Sulphate from fossil fuel burning

• The increased debris and dust from a volcanic explosion will have a negative albdeo affect • Meaning more light is reflected and there will be cooling

• Instrumental records (350yrs max, but genrally less than 150yrs) • The past c.1000yrs (tree-rings, ice-cores etc) • Long-term variability on any timescale over which reliable data can be obtained (Lake sediments, ice cores, fossils etc)

That different GHG will produce different amounts of warming measured by his radio spectrophotometer

• Daily measurements of CO₂ taken at the Mauna Loa Observatory in Hawaii • Daily fluctuations due to photosynthesis ceasing in the nightime • Record goes back to 1958

In 1974

• By selecting a reference year (or period which has been average) • And subtracting it from each annual temperature measurements • Hence allows a trend to be worked out like this

• Hard to read thermometers to an accurate degree (e.g. there has only been 0.8°C warming in past 150yrs) • Different countries may have different resources and different ways of doing things • Hence need for standardisation is important

• Radom error are tolerable, if you have a long enough record to make good averages (anomalies can be spotted easily) • Systematic changes over time must be identified and corrected if possible e.g. Urban heat island effect