CHAPTER 16:GLOBAL

WARMING

Global Change

• Changes in environmental processes affecting the whole Earth• Temperature changes in the last decade.

Which part of Canada has seen the greatest temperature changes?

Why study global change?

• Atmospheric CO2 concentration exceeded 400 ppm in May of 2013 – higher than at any other time in past 15 million years.

• 2010 is the hottest year on record, and 2007 is the second hottest • 12 out of the 13 hottest years

ever recorded have taken place since 2001

• We are not even close to seeing the full effects of 400 ppm CO2. 15 million years ago, when the climate was in equilibrium with similarly high CO2 levels, sea level was 23 to 36 m higher than it is now, and the global temperature was 2.8°C to 5.5°C warmer.

Definitions

• Global warming – increase in the average temperature of Earth’s surface– (including the oceans)

• Climate– long-term (~30 years) average weather pattern in a particular region resulting

from interactions among land, ocean, atmosphere, ice, and the biosphere

• Global climate change– any large-scale change in climate over time, whether natural or as a result of

human activity

Earth's 7.2 billion people are using natural resources 23% faster than the natural renewal rate!

Is our use of natural resources sustainable? Is it justifiable?

Heat Circulation in the atmosphere and oceans maintains Earth’s climate

• Climate Change is caused by changes in the way this heat moves and accumulates in the atmosphere...

Thermohaline Circulation

• ... and in the Oceans.

Circulation patterns in the troposphere

The greenhouse effect is at the heart of Earth’s climate system

• The greenhouse gases of our atmosphere have the ability to absorb and store heat radiated from the surface of the Earth

• The greenhouse effect maintains Earth’s average temperature at ~14°C (conditions conducive to life)

• Without the greenhouse effect Earth’s average temperature would be -18°C

Earth's heat budget

Greenhouse Gases

• Absorb long-wave radiation (IR energy radiated from the surfaces of the earth that have been warmed by the sun)

• Represent ~1% of the atmosphere Water vapor (H2O) Carbon Dioxide (CO2) Ozone (O3)

Methane (CH4)fluorocarbonsNitrous Oxide (N2O)

The composition of the atmosphere (excluding H2O). The greenhouse gases ozone, fluorocarbons and nitrous oxide are included in “others”. Their proportions are small, but their effect is real.

(0.04%)

Stev

en E

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The Rise in CO2

• Today's carbon dioxide level of 400 ppm is well above natural levels for the past 400,000 years, as shown here, and in fact for the past 15 million years.

What is the explanation for the cyclical patterns of past temperatures

and GHG levels?

Important greenhouse gas concentrations in Earth's atmosphere from 1978 to 2010

The global carbon cycle describes how carbon moves through natural systems

What is the largest reservoir of carbon according to this diagram?

Carbon is found in many forms ...

• Rocks in the lithosphere• Carbon dioxide dissolved in water• Organic matter in the biosphere and the lithosphere• Gases in the atmosphere• but most carbon is stored in rocks

A limestone mountain in the southern Rockies near to the BC-Alberta border

Climate modeling

• Climate modeling improves our understanding of global change

Actual T changes ( ) are most closely represented by models that consider anthropogenic forcings

Parallels

• Atmospheric CO2 levels kept pace with the warming climate of the last de-glaciation and the steady climate of the Holocene interglacial, but the change in CO2 levels over the past century has no parallel in the geological record.

400 ppm in 2013

What is the cause of the huge spike in CO2 levels over the past century?

The Increase in CO2 Levels

• The human contributions to the dramatic increase in CO2 levels are primarily due to:

• The burning of fossil fuels

The Increase in CO2 Levels

• Deforestation and the burning of organic biomass

The Increase in CO2 Levels

• and the production of cement.

Limestone quarry and cement plant near to Exshaw Alberta in the Canadian RockiesSteven Earle

The Increase in CO2 Levels

• In the last 200 years atmospheric carbon dioxide levels have risen by almost 50%.

• In the last 70 years natural resource use has increased ten-fold and the human population has tripled.

• ~83% of global human greenhouse gas emissions are produced by 25 countries and ~42% are produced by just 2 countries.

Which two countries are responsible for 42% of global GHG emissions?

Population growth is a major part of the problem

Population growth(global)

Percentage of growth(annual)

These are global figures. There are regional variations

related to automobile use and

methods of electricity

generation.

How might the numbers for your

region be different than these?

Earth’s average temperature has risen by over 0.8°C in the past 100 years

Past Temperature

• Earth’s average temperature dropped very slowly over the 1200 years from 700 to 1900 AD, but has increased quickly since then.

Annual Sea Ice Minimum

• The Arctic has warmed by ~2.7°C in the last 30 years, considerably more than other parts of the Earth. One reason for that is the loss of approximately half of the permanent Arctic sea ice over that time.

Why might sea-ice loss have such a dramatic effect on the climate of the Arctic region?

Sea level rise accelerated over the period since 1996

Global warming leads to…

• ocean warming and acidification

What is the problem with ocean acidification?

Global warming leads to…

• loss of glacial ice

Global warming leads to…

• Sea level rise

Steven Earle

Global warming leads to…

• Changes in extreme weather

Global warming leads to…

• Degradation and shrinkage of wildlife habitats• Changes in the distribution of food sources• Disruption of the timing of migration patterns• Increased range of pest insects (e.g., mountain pine beetle)• Desertification• Increase in the incidence of slope failures because of heavy precipitation

Several international efforts focused on understanding and managing climate change

• Intergovernmental Panel on Climate Change (IPCC)• The Kyoto Protocol

– Carbon quotas– Emissions trading

• But many individuals, corporations and governments show no interest in taking the decisive action that will lead to the needed changes.

What type of individual actions (lifestyle changes) can you take to reduce your personal contribution to climate change?

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