Evidence of Climate Change

We all have heard the term ‘global warming’ but is there any evidence that our climate is changing?

1. Melting Ice

Many glaciers that have been getting smaller recently

1890

1990

parts of Antarctic ice sheet are breaking up

1988 2008

2. Rising sea Levels

Higher sea levels means more flooding

The total number of storms has not varied over time BUT

The number of short-duration SEVERE storms has increased

3. Storm Intensity

4. Coral reef size

Coral reefs have been shrinking in most places.

Area covered by coral reefs in four parts of the Caribbean as measured over time.

What evidence is there that climate has been changing over longer periods?

All of these changes have been recent, 100 years or so!

5. Fossil records

Fossil of a tree from Antarctica, an area far too cold for modern forests

6. Tree Rings (or dendrochronology)

relative growth of trees each year gives clues to climate conditions in the past

How far back does this record go?

1000 years? quite a few trees this old

5000 years? a few trees this old

10000 years? no trees this old

but can use old dead trees to go back this far

The problem with tree rings is they only give us clues as to how well the tree grew at that time.

They give us no other information about the other conditions at that time.

Researchers want to see into the past and find more than just temperature data.

Where can they look? What should they look for?

7. Ice Core Data

drill down into glaciers or ice sheets

Like trees, ice cores have ‘rings’

analysis of these ‘rings’ allows researchers to determine

there is gas trapped in the ice past atmosphere gases

melt & freeze patterns and O2 isotopes past temperatures

[Antarctica]

Results?

temperature has varied over the past 400,000 years

It has been up to 4oC warmer and 8oC cooler than now

CO2 levels have also varied over the past 400,000 years

The question is, are the variations related?

When CO2 is low, temp is low When CO2 is high, temp is high

Have any other gases varied over time? Yes!

Nitrous oxide (NO) has increased a lot since 1800’s

methane (CH4) has increased a lot since 1800’s

sulphate (SO4) ions have increased a lot since 1800’s

Note that all four gases show similar patterns

and all correlate to increases in temperature

Are all of these changes that we have seen related?

ice melting, rising sea levels, more intense storms

shrinking coral reefs

All result from warmer temperatures

CO2, N2O, CH4 and SO4 gases are all natural greenhouse gases involved in Earth temperature

Therefore the question now is what is causing all of these changes?

The causes of these changes in climate

1. Natural fluctuations

We know that CO2 does naturally vary a lot

2. Anthropogenic cause (man-made)

Most of the observed changes have happened in the past 250 years.

So what happened about 250 years ago?

watermill

windmill

As long as we needed only a small source of power,

water, wind or horses were enough

To operate a large mill or factory, you need the power of steam.

And you make steam by boiling water

We used to burn wood,

but burning wood is not very efficient

We switched from burning a small amount of wood.

To burning a large amount of coal.

To power the factories and the mills of the Industrial Revolution

initially coal was main energy source

and remains a big source

but now oil and natural gas are also big