Physics of Planetary ClimateCors221: Physics in Everyday Life

Fall 2010 Module 3

Lecture 9: Consequences of Global Warming

From Last Time•Glaciers melted off rapidly at the start of this interglacial ~15000 years ago. Brief reversion during Younger Dryas perhaps due to stopping of the thermohaline ocean circulation.•General slow decline since onset of present interglacial.•Instrumental temperature record shows warming since 1900 or so.•Satellite temperatures show warming trend since late 1970s. Planetary temps have been pretty flat last 10 years – statistical outlier?•Carbon Dioxide and other greenhouse gases have sharply increased in concentration over the past 150 years.•Satellites have directly measured a decrease in Earth’s emitted infrared blackbody spectrum resulting from increased absorption due to carbon dioxide, methane, and other greenhouse gases.•Patterns of planetary temperature are consistent with a greenhouse origin to the warming.

CO2 Projections

Planetary Average Temperature Projections

Warming is Non-Uniform

1. * Preferentially affects daily LOW temperatures

1. * Preferentially affects POLAR regions

Warming is Non-Uniform

Nonlinear Effects: Gulf Stream

Younger Dryas – Gulfstream Shutdown?

Nonlinear Effects: Rainfall

Nonlinear Effects: Hurricanes

Nonlinear Effects: Hurricanes

Consequences for Agriculture

Consequences for Agriculture

Consequences for Agriculture

Consequences for Ecosystems

Consequences for Ecosystems

Glacial Melting

Glacial National Park

North Polar Sea Ice

North Polar Sea Ice

North Polar Sea Ice

Global Sea Level Predicts

Key Points•For a wide range of carbon dioxide emission scenarios, global average temperatures are predicted to rise 2-4oC (4-7oF) by 2100.•Be careful with these global average temperature numbers. This higher average is driven primarily by higher nighttime low temperatures and higher polar temperatures.•Warming can also cause nonlinear effects, like changes in air and ocean circulation that can have large climate effects over subcontinent-scale regions.•Warming can also lead to changes in rainfall patterns, like increased or decreased rainfall, fewer but more intense storms, and more big hurricanes.•Ecosystems will shift, some will vanish, some new ones created. This would cause some extinctions.•Particularly worrisome is the prospect for reduced agricultural output as optimal growing zones move, change size, and/or disappear.•Melting of land ice and heating of oceans will cause sea level rise.