The Anthropogenic Greenhouse Effect Climate Change: Lesson#3

Climate History in a Tree Trunk Recording growth is one way to document change. The growth of a tree is documented in the widths of its rings. One tree ring is formed every year, during the summer when the tree grows. Thicker rings mean the tree grew in better conditions; enough precipitation and appropriate temperatures. Thin rings mean poorer conditions: drought, or higher or lower temperatures than usual.

History in a Tree Trunk By comparing the rings, scientists can determine the weather conditions over the life of the tree. Since some trees live for hundreds of years, the rings provide “long- term” climate data.

History in Coral Reefs Corals add layers of growth each season Studied by drilling cylinders Temperature of surface water is obtained as coral growth depends on water temperature History in Coral Reefs 4 4

Greenhouse Gases Last lesson we learned that the natural greenhouse effect keeps the planet warm by absorbing radiation from the sun and re-emitting it as thermal energy The natural greenhouse effect is due mainly to the presence in our atmosphere of water vapour, with other naturally occurring greenhouse gases, such as carbon dioxide, methane, and nitrous oxide, also playing a role These gases are also produced by human activities, such as industry, electricity generation, transportation, and agriculture

Greenhouse Gases The principal greenhouse gases that trap infrared radiation in the atmosphere are: Water vapour Carbon dioxide Methane Chlorofluorocarbons (CFCs) Ozone Nitrous oxide

Global Warming Potential over 100 years Greenhouse Gases Persistence is the length of time a gas remains in the atmosphere. Gases that persist longer can absorb thermal energy over a longer period of time. Persistence of carbon dioxide is not defined because it depends on the amount emitted and carbon dioxide has a variety of sinks (places of storage). Global warming potential is a measure of the ability of a gas to trap thermal energy in the atmosphere over a specified time….. Gas Global Warming Potential over 100 years Persistence (Years) Carbon Dioxide CO2 1 - Methane CH4 25 12 Nitrous Oxide N2O 298 114

History of Greenhouse Gas Research The discovery that different gases absorbed radiation differently dates back to the work of the Irish scientist John Tyndall in 1861. In the first half of the 20th century climatologists noticed that the average global temperature was rising slowly They measured concentrations of different gases in the atmosphere over time and found that CO2 & CH4 (Carbon dioxide & methane) levels were increasing However, they had no previous data to give them a complete history of the gases in the atmosphere

Greenland Ice Core Project (GRIP) Climatologists discovered that atmospheric gas data could be extracted from the continental glacier in Greenland, a glacier that had been there for 200 000+ years. Each year’s snowfall is recorded as a distinct layer. From 1989 to 1992, a 3029-m-long ice core was drilled vertically and removed from the continental glacier. At its deepest, the ice layer is thought to be 200 000 years old, while the ice layer at the surface was formed the previous winter..

Greenland Ice Core Project (GRIP) Ancient ice can be studied because air at the time of freezing is trapped in the ice and can be analyzed for CO2 concentrations. It was found that CO2 remained stable for 10,000 years at 280 ppm, then around 1750 (Industrial Revolution) CO2 began to rise rapidly to its current state of 385 ppm. Ice Cores Greenland Ice Core Project (GRIP)

Increasing Greenhouse Gas Concentrations The data from ice-core samples from Greenland and Antarctica, & atmospheric data collected over the last few decades have led climatologists to conclude that: greenhouse gases in the atmosphere have increased since the 1700s

Greenhouse Gases & Human Activity These conclusions have indicated that the increase in greenhouse gas levels are a direct result of changes in human activity Before the industrial revolution (1870) humans depended on manual labor, animals for transportation and labor, wind power, and water power to do work and produce goods During the Industrial Revolution, the focus shifted rapidly to coal-fired steam engines and the mass production of goods. Human society became more and more dependent on the consumption of fossil fuels.

Since greenhouse gases absorb heat, changes in their concentrations disrupt the radiation balance on Earth Increased greenhouse gases mean that less thermal energy is released back into space, and as a result, the average temperature of the Earth’s surface increases

The Anthropogenic Greenhouse Effect The additional greenhouse gas emissions are causing the anthropogenic greenhouse effect: which is the enhancement of the natural greenhouse effect due to human activities. The most significant greenhouse gas is carbon dioxide, CO2 Any process that releases carbon dioxide to the atmosphere is called a carbon source. Example: Burning fossil fuels & the respiration of organisms

Sources of Greenhouse Gases Fossil Fuels: Coal, oil, and natural gas – formed underground from the remains of once living organisms. Made up of Carbon, hydrogen & Oxygen (hydrocarbons) When burned, large amounts of CO2 and N2O are produced. For every litter of gasoline burned, 2.3kg of CO2 is produced.

Unnatural Sources of Greenhouse Gases Carbon dioxide CO2 (72% of total) Burning coal, oil, gasoline, and natural gas Cement making Deforestation Methane CH4 (18% of total) Production of petroleum products Farming, landfills, cattle Natural gas leaks Coal mining Nitrous Oxide N2O (9% of total) Fertilizer

Unnatural Sources of Greenhouse Gases For this reason we differentiate the natural greenhouse effect from the anthropogenic greenhouse effect (the excess GHGs produced by human activities).

Rising Concentrations of CO2 And carbon dioxide levels have been rising: This famous graph is known as the Keeling curve.

Greenhouse Gas Sinks Forests play an important role in removing carbon dioxide from the air through the process of photosynthesis. Photosynthesis is a carbon sink Carbon sinks: Mechanisms that remove carbon dioxide from the atmosphere (ex. Forests, Oceans & Lakes, Soil) A significant fraction of the increase in carbon dioxide can be attributed to deforestation (CO2 has increased by 38% in the last 200 years)

The Annual Carbon Dioxide Cycle Carbon dioxide levels decrease during the spring and summer months because that is when the Northern Hemisphere (most of the world’s landmass) is experiencing growth in carbon-dioxide absorbing vegetation. http://www.youtube.com/watch?v=l8tPK j20GFo

Greenhouse Gases, Global Warming, and Climate Change Climate scientists have concluded that the increased emissions of greenhouse gases by human activity have influenced the global climate. The anthropogenic greenhouse effect is a change in Earth’s net radiation budget caused by the increase in human-generated greenhouse gases.

Greenhouse Gases, Global Warming, and Climate Change Temperature data from around the world has shown that the average global temperature has raised by ~1 Degree Celsius over the last century. This timespan was also the period in which humans went through the industrial revolution (invention of combustion engine, burning of fossil fuels) Temperatures from 1880 to 2008 indicate that the 8 warmest years have all occurred since 1998.

Greenhouse Gases, Global Warming, and Climate Change This warming trend is known as global warming: The observed increase in Earth’s average annual temperature Global warming is leading to climate change: The significant long-term change in expected climate patterns.

Effects of Climate Change Climate change means that more than just temperature is changing, In general, the world is experiencing more extreme conditions: Increase in the number and severity of storms Increase in the strength of winds Melting Polar ice caps, and mountain glaciers ->Rising global sea levels, reduction is fresh water Changing amounts of precipitation, contributing to both floods and droughts Effects of Climate Change

Effects of Climate Change Animals moving farther north to account for warmer climate Vanishing species in the Northern biomes of the world Increase in related economic problems Increase in health risks (i.e. malaria breeding grounds, heat stress, drinking water conditions…)

A Global Problem An important international organization that has noted the change is the Intergovernmental Panel on Climate Change (IPCC) A group of the world’s leading climate scientists from many countries brought together by the World Meteorological Organization (WMO) and the United Nations Environment Program (UNEP). The IPCC has linked global warming to the increase in the amount of greenhouse gases in the atmosphere. If we continue living like we are, now, global warming will happen even faster.

Human Activities Contribute to Climate Change The generation of electricity, transportation and industry produces large amounts of CO2, but lifestyle also contributes to the greenhouse gases. We live in a disposable society where everything is thrown out. Landfills compress the garbage; bacteria break down the garbage and produce methane gas. By reducing consumption we can help to reduce our carbon footprint.

Human Activities Contribute to Climate Change

Questions Complete your worksheets and hand in by the end of class! (pgs 323-339 of text might help)