Causes of Climate Change and evidence

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Patterns in Environmental Quality and Sustainability:

Patterns in Environmental Quality and Sustainability Atmosphere and Change

Learning Objectives:

Learning Objectives

Short Term Objective 1.:

Short Term Objective 1. Describe the functioning of the atmospheric system in terms of the energy balance between solar and long-wave radiation.

What do you know already:

What do you know already Draw a fully labelled diagram to show the causes of climatic change. You can do this as a group

What are the percentages?:

What are the percentages? The Earths atmosphere is an example of an open system – what does this mean and why is it important? The Greenhouse effect is natural and important to the earth. Why?

Albedo may affect the energy balance between short and long term radiation:

Albedo may affect the energy balance between short and long term radiation What is albedo? Use figures from the table above to describe how the albedo of the atmosphere can change the amount of solar radiation arriving at the ground surface. Use figures from the table above to describe how the albedo of the ground surface can change the amount of long wave radiation emitted by the earth

If the Greenhouse effect is natural then what’s the problem?:

If the Greenhouse effect is natural then what’s the problem?

Climate changes all the time but what has happened recently?:

Climate changes all the time but what has happened recently? The problem is that the rate of change seems to have risen rapidly since the Industrial Revolution. Hence it is sometimes called the enhanced Greenhouse Effect. Why?

The causes of climate change – Build up of Greenhouse Gases:

The causes of climate change – Build up of Greenhouse Gases Read about the main greenhouse gases on page 32 and make notes on them

Slide 11:

Climate Change is not a new thing! The worlds climate has been changing over the last 18 000 years, sometimes getting hotter and sometimes colder as you can see from the graph below.

Slide 12:

Even over short periods there are fairly large fluctuations

Slide 15:

Is climate change natural or human induced (anthropogenic)? There are 3 main natural ways that scientists believe affect the worlds climate 1 Variation in the earths orbit 2 Variation in solar output 3 Volcanic eruptions and cosmic causes

1: Variations in Solar Output:

1: Variations in Solar Output The sun’s output is not constant is also varies. A variety of cycles have been detected, most are short term, the most obvious is due to sun Spot activity – 11yrs The effect of sunspots is to blast more solar radiation towards the earth Some scientists have suggested that around 20% of 20 th Century warming may be because of solar output variation However a study in 2006 showed no major increase in solar output since mid 1970s

Slide 17:

What are sunspots? How are they linked with the amount of solar radiation the earth receives? Describe the pattern of sunspot activity. What is the link between sunspot activity and global temperature anomalies?

2: Variations in the Earth’s Orbit:

2: Variations in the Earth’s Orbit Milankovitch Cycles A Serbian physicist working at the beginning of the 20 th century. He identified 3 variations in the Earth’s orbit around the Sun Link Milutin Milankovitch 1879 - 1958

Eccentricity:

Eccentricity Every 100,000 yrs the Earths orbit changes from spherical to elliptical, changing solar input

Tilt of the Earth:

Tilt of the Earth The Earth’s axis is tilted at 23.5 o , this changes over a 41,000 yr cycle between 22 o & 24.5 o, affecting solar input, especially in higher latitudes.

Wobbly axis!:

Wobbly axis! The Earth’s axis wobbles, so which way the hemispheres are facing to the sun when closest to the sun varies over 21,0000 yrs . Affecting solar input.

Slide 22:

Milankovitch Cycles Many scientists argue that the Milankovitch cycle may have been just enough to trigger a major global climate change, but that climate feedback mechanisms are needed to sustain it. KEY WORD: Feedback effects are those that can amplify a change and make it bigger (positive) or smaller (negative). An e.g. of positive feedback is snow and ice cover. Small increase in snow and ice raises surface Aledo reflecting more solar energy back into space. Resulting in further cooling An e.g. of negative feedback s cloud cover. As GW occurs, more evaporation occurs increasing cloud cover, which in turn may reflect more solar rays back into space diminishing effects of the warming. Also Siberian Tundra?? What about it

3. Volcanoes and cosmic collisions:

3. Volcanoes and cosmic collisions Major eruptions eject material into stratosphere. The sulphur dioxide forms a haze of sulphate aerosols, which reduces the amount of sunlight received at Earth’s surface The eruption of Tambora led to the year without a summer in 1816 as global temperatures dipped by 0.4-0.7 degrees C An asteroid smashing into the Yucatan peninsular is though to have led to dinosaur extinctions.

Slide 24:

Unprecedented Global warming? What does this phrase mean?? Never been seen before! So is Global warming unprecedented? Not unprecedented as we have had changes before where periods of time have been warmer. However, the quote from the IPCC in 2007 sums up the current views on Global warming: “ The observed widespread warming of the atmosphere and ocean, together with ice mass loss, support the conclusion that it is extremely unlikely that global climate change of the past 50 yrs can be explained without external forcing , and very likely that it is not due to known natural causes alone”

So anthropogenic causes seem to be confirmed! Note down some of the recent facts to emphasize this!:

So anthropogenic causes seem to be confirmed! Note down some of the recent facts to emphasize this! The level of CO2 in the atmosphere is far above the ‘natural’ level and continues to rise. 11 of the 12 warmest years on record occurred between 1995 and 2006 Temperature rises have been recorded on all continents since 1970 Satellite observations since 1993 suggest an annual rise in sea level of 3.1mm, and a decline in Arctic sea ice of 2.7% per decade

Slide 26:

Where do we get the long term evidence for climate change from? 1. Ice Cores Best evidence for climate change comes from Greenland and Antarctic ice cores Ice cores are a frozen record of past climates. Like a time capsule!! Within these layers the ice contains air bubbles which contain carbon dioxide and oxygen isotopes.

Slide 27:

What is the Evidence for Long Term Changes in Climate

Slide 28:

1. Ice Cores From looking at the graph below you can see clearly the periods of low concentrations of CO2 occur during glacial periods High concentrations of CO2 link with warmer periods of time- like the Holocene interglacial we are going through now!

Slide 29:

1. Ice Cores- How accurate and reliable are these sources of data? The sequences of sea level change links very closely with oxygen and CO2 isotope levels suggesting that this is a very reliable source!

2. Pollen Analysis:

2. Pollen Analysis Pollen is produced by all plants and was extracted from sediment cores in peat bogs and lake beds. Pollen grains are preserved in waterlogged sediments. By analysing Pollen we can see how ecosystems have changed in response to climate change.

Slide 31:

2. Pollen Analysis- How accurate and reliable are these sources of data? Not as reliable - as accurate pollen reconstructions rely on good preservation of pollen. Long pollen sequences are rare, and vegetation change may lag behind “climate change”.

Where do we get the medium term evidence for climate change from?:

Where do we get the medium term evidence for climate change from? 1. Tree Rings (Dendrochronology) Many trees are sensitive to changes in temp, sunlight and precipitation In warm years trees have wide rings & vice versa Record can go back 10,000years+

Slide 33:

1. Tree rings- How accurate and reliable are these sources of data? Good reliability – However, tree records only give localised records!

2. Paintings and written accounts:

2. Paintings and written accounts Bruegel Painting 1565 London Frost Fair 1789 6b. Paintings are a good line of evidence

Dickensian Winters:

Dickensian Winters 6c. The written word is also good evidence

Slide 36:

2. Historical records- How accurate and reliable are these sources of data? Unreliable – These sources did not set out to record climate, and must be used with care. They are usually local, and difficult to generalise.

3. Glacier Retreat:

3. Glacier Retreat

Slide 38:

3. Retreating glaciers Glaciers change in response to climate change. We can look at old photos/maps/paintings to measure direct differences in glacial positions

Slide 39:

3. Retreating Glaciers- How accurate and reliable are these sources of data? Reliable – Good records stretch back to around 1880, before this the record is patchy.

Slide 40:

The last 128yrs of data suggest the Earth is 0.7 – 0.8 o C warmer 11 of the world’s hottest 12 years occurred in the decade 1995-2006 Global warming or natural? Where do we get the short term evidence for climate change from?

Short Term:

Short Term Link between CO 2 & temperature Is the Carbon Anthropogenic (human) or Natural? Most scientists agree Anthropogenic

Short Term:

Short Term 3 possible effects of climate change!

Homework:

Homework Beg borrow or steal a copy of “the inconvenient Truth” Watch it and fill in the sheets ready for discussion next lesson.

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