Changing Climate

Define climate change

large scale, long-term shift in the Earth's temperature and precipitation patterns

Define weather

the day to day changes in atmospheric conditions

Define climate

the average weather conditions over time (usually calculated over a 30 year period)

How long is the Quaternary period?

the last 2.6 million years

What has Earth's climate been like over the Quaternary period?

global temperatures have fluctuated from colder glacials to warmer interglacials

What is an ice age or glacial period?

a cold period in earth's climate when ice sheets and glaciers spread from the Poles, sea levels fall, continents become connected

What is an inter-glacial period?

a warm period in earth's climate between glacial periods when ice melts and retreats to leave new rivers + lakes and animals return to higher latitudes

What is global warming?

a trend associated with recent climate change involving a warming trend (0.85°C since 1880)

What are some key pieces of evidence of climate change?

1. Global Temperature Records

2. Tree rings

3. Ice cores

4. Historical records

5. Microfossils

How do ice cores show climate change?

Trapped air bubbles in the ice show that CO2 levels have fluctuated from 180ppm to 280ppm over the last 800,000 years.

How do microfossils show climate change?

Different species prefer different climates

How do ocean sediments show climate change?

organisms in sediment reveal past temperatures, levels of oxygen and nutrients

How does 'The little Ice Age' show evidence of natural climate change?

Between 1300-1870 Europe experienced winter temperatures considerably colder than today. During this period impacts included:

1. Price of grain increased and vineyards become unproductive and food stocks were limited.

2. Frost Fairs were held on rivers such as the River Thames.

What are the 3 Milankovitch cycles, and on what time periods do they operate?

1. Eccentricity (orbit) - 100,000years

2. Obliquity (tilt) - 41,000years

3. Precession (wobble) - 26,000years

How does eccentricity (orbit) affect climate?

In this 100,000 year cycle the Earth's orbit changes from circular to elliptical and back to circular again. Colder periods occur when the orbit is more circular.

How does precession (wobble) affect climate?

26,000 year cycle during which the axis of the Earth shifts. This affects timings of seasons and how much solar energy each hemisphere receives

How does obliquity (tilt) affect climate?

41,000 year cycle during which the tilt of the earth cycles from 21.5 degrees to 24.5 degrees and back again.

Caused by gravity of large planets and causes changing seasons and strength of seasons

external forcings

factors causing climate change occurring outside the Earth’s atmosphere

internal forcings

factors causing climate change occurring inside the Earth’s atmosphere

climate forcings

factors causing climate change

How do volcanic eruptions affect climate?

1. Sulphur dioxide emitted in eruptions helps to reflect sunlight and encourage clouds to form which cools the atmosphere for a few years.

2. They release the greenhouse gas carbon dioxide, contributing to warming of the atmosphere. But the warming effect is very small.

How did Mount Pinatubo eruption affect earth's climate?

• Volcanic ash cloud blocked solar energy reaching earth

• It released sulphur dioxide which dissolved to become acid rain and reflect solar energy

• average global temperature fell 0.5C for 2 years

asteroid impacts on climate change

dust and gas thrown up in air blocks solar energy

How do sunspots affect Earth's temperature?

a spot or dark patch that appears on the surface of the sun and is associated with an outburst of energy from the Sun, making it temporarily warmer

Maunder minimum

period lasting 70 years from 1645 - 1715 during which sunspot activity was low

solar output

The amount of energy and heat the sun emits is different at times

What is the greenhouse effect?

• short wave radiation from Sun reaches Earth

• 30% reflected by ice caps, deserts due to albedo effect

• 70% re-emitted as long wave radiation

• some are trapped and absorbed by greenhouse gases in atmosphere and keep Earth warm enough to sustain life

What is the enhanced greenhouse effect?

an increase in humans burning fossil fuels and deforestation have emitted extra greenhouse gases. Consequently earth's atmosphere traps more solar radiation and is becoming warmer.

carbon sink

a forest, ocean, or other natural environment viewed in terms of its ability to absorb carbon dioxide from the atmosphere.

carbon source

where carbon accumulates and is released

stores of carbon

CO2 in atmosphere

organisms

fossil fuels

effect of burning fossil fuels

removes ground carbon store and increases CO2 in atmosphere

effect of agriculture

How much has global sea level risen by in the last 100 years?

10-20cms

What are the causes of global sea level rise?

1. Thermal expansion

2. Melting glaciers and ice sheets

How does thermal expansion raise sea levels?

As the temperature of the ocean increases the volume of water increases, raising sea levels