Global Climate Change

What observations lead scientists to believe that global climate is changing? What are the hypotheses that have been proposed to explain these observations?

NOAA Reconstruction - Global 20 warmest years since 1880 (Current to 2013) Year °C Anomaly from Mean

How can we explain this observation? Greenhouse Gasses Much of the sunlight that enters our atmosphere is reflected back out to space as infrared radiation GHGs are any gasses that absorb this radiation, trapping the heat in our atmosphere

Since the Industrial Revolution, atmospheric concentrations of greenhouse gasses have increased dramatically. –Carbon dioxide (CO2) concentrations have increased 33% –Methane (CH4) concentrations have increased more than 100% –Nitrous oxide (N20) concentrations have increased by about 15%

Total CO2 emissions for the US alone in 2012: 5,376Tg or 5,760,000,000,000,000 grams (A teragram (Tg) is equal to 1x10 12 grams; 1,000,000,000,000 grams) 5,065Tg of that was fossil fuel combustion –2,023Tg from electricity generation –1,735Tg from transportation –769Tg from industry –The remainder from homes and businesses Annual EPA Inventory of US Greenhouse Gas Emissions 2014

In contrast, volcanoes worldwide release an annual average of 37Tg

As CO2 builds up in the atmosphere, average global temperature rises. As demand for energy grows, CO2 emissions increase. As population grows, demand for energy grows.

How about natural cycles? Can they explain the warming we see? Earth’s climate very definitely goes through regular and predictable cycles

Natural cycles are caused by phenomenon such as obliquity (how the Earth tilts on its axis) and eccentricity (variation in orbital pattern) that are well understood and predictable using modern physics.

Based on the physics of natural cycles, we should actually be entering a period where average global temperatures cool. Instead, we see the opposite as global average temperatures increase despite natural cycles. Based on the data, is the hypothesis of increased greenhouse gas emissions or natural cycles better supported as driving global climate change?

Go to “Climate Time Machine”: Pair up at a computer and go watch each of the four scenarios. Record your thoughts for each scenario on the worksheet provided. 2.Group up with the other pair at your table. Share your thoughts for each scenario. Pick a scenario you want to be responsible for proposing a solution to and mark it on your worksheet. 3.As a group, illustrate a poster with each of the four scenarios and a solution. 4.Present your solutions to the class (each of you present the solution to the scenario you are responsible for).