Climate Change – Examining the Evidence Chapter 3

Objectives describe the composition of greenhouse gases relate incidence of greenhouse gases to human activity describe the relationship between greenhouse gases and climate change discuss international collaboration on climate change, including specific programs assess the impacts of climate change

Greenhouse Gases Natural greenhouse effect  keeps planet warm by absorbing some of the thermal energy radiated from the Earth Caused mainly by water vapor Four main greenhouse gases: Water vapor CO2 Methane Nitrous oxide (N2O)

Global Warming Potential Gas Global Warming Potential Persistence (years) Carbon dioxide 1 50-200 Methane 23 10 Nitrous oxide (N2O) 296 120 Global warming potential  measure of ability of gas to trap thermal energy  CO2 most common; everything measured against it Persistence  time gas remains in atmosphere

Enhanced Greenhouse Effect There is a necessary amount of global warming that makes our planet inhabitable. Current global average: 15°C With no carbon dioxide or water vapor in the air: -18°C

Enhanced Greenhouse Effect This enhanced greenhouse effect is referring to the greater amount of carbon (in the form of CO2 ) that is being put into the atmosphere.

Enhanced Greenhouse Effect Water vapour is one of the natural green house gases present in the atmosphere. Water vapour lasts about 10 days in the atmosphere before falling as precipitation.

Enhanced Greenhouse Effect Water vapour may only last 10 days in the atmosphere but it makes up 65% of the greenhouse gases. With enhanced global warming there might be more evaporation of water.

Enhanced Greenhouse Effect All of the greenhouse gases differ in many different ways: Their global warming potential Their length of time in the atmosphere Rate of addition to the atmosphere. Effect on other gases in the atmosphere.

Carbon and Carbon Dioxide Carbon is found in a variety of forms on the planet. Carbon dioxide in the atmosphere Carbonates in rocks Carbon in fossil fuels, and natural gas In organisms as carbohydrates, lipids, proteins

Carbon and Carbon Dioxide The movement of Carbon through the biosphere is referred to as the carbon cycle. Each year about 158 Gigatonnes of carbon move through the biosphere 1 Gt = 1,000,000,000 tonnes

Increasing CO2 in the Atmosphere The ice core findings we discussed revealed levels of carbon dioxide that were extraordinarily high. Since the 1960s CO2 in the atmosphere has gone up from 320 ppm to 390 ppm now.

Increasing CO2 in the Atmosphere The main reason for this increase is the burning of fossil fuels, and the removal of trees. Carbon sinks are large storage places for carbon compounds. Rocks and oceans are the largest sinks. Why are humans continuing to do these things if there is an increase in CO2?

Plants and CO2 The presence of large amounts of plants can help reduce the amount of CO2 During photosynthesis CO2 combines with water to make sugars. Deforestation has a large effect on the amount of CO2 present.

Other Greenhouse Gases Heat Trapping Ability to CO2 Atmospheric life span (years) Concentration in PPM 2012 Contribution to global warming Origin CO2 1 2 – 3 280 390 60% Mostly human Methane (CH4) 23 8 0.7 1.76 20% Natural and human Dinitrogen monoxide (N2O 296 120 0.275 0.316 6% CFCs 12400 50 0.000272 4% Human

Greenhouse Gases See that concentrations of greenhouse gases in ice cores have increased since about 1700 What historical event occurred then? Industrial Revolution  increase in fossil fuel consumption What is a fossil fuel? Fuel with lots of carbon, formed from living organism remains Coal, oil and natural gas Releases all three greenhouse gases

Greenhouse Gases and Human Activity What does this mean overall? Increased greenhouse gas levels mean that less thermal energy is released back into space Average temperature of Earth rises

Carbon Sources and Sinks Carbon source  process releasing CO2(g) to atmosphere Includes burning fossil fuels and respiration Carbon sink  removes CO2(g) from the atmosphere Photosynthesis Dissolved CO2(g) in oceans and lakes How are we increasing CO2(g) in the atmosphere? Forest removal Agriculture Garbage (releases nitrous oxide)

Halocarbons Human-made chemicals Absorb significant amounts of thermal energy Used as coolants Fridges, air conditioners CFCs  class of halocarbons Global warming potential of 12 000 Used to be in aerosols Restricted use Contribute to the destruction of ozone http://www.cbc.ca/news/technology/story/2011/06/03/technolo gy-ultraviolet-ozone-sun-summer.html

Greenhouse Effect and Climate Change What is the greenhouse effect? Global warming  observed increase in Earth’s average temperature Important detection organization: IPCC (Intergovernmental Panel on Climate Change) Operates out of UN If we continue with our current practices, global warming will continue and result in climate change

Other Evidence Flowers in Northern Hemisphere blooming 26 days earlier Severe weather-related disasters Amount of snow cover and ice has decreased Level of oceans increased 2-5 cm

Evaluating Evidence of Climate Change Study of climate change challenging Confidence rating  probability that result is true Analyses and predictions have higher confidence ratings with More data More accurate measurements Good understanding of factors involved Ex. Have high confidence rating for increasing greenhouse gases