Cors221: Physics in Everyday Life Fall 2010 Module 3 Lecture 9: Consequences of Global Warming Physics of Planetary Climate
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.
Planetary Average Temperature Projections
* Preferentially affects daily LOW temperatures * Preferentially affects POLAR regions Warming is Non-Uniform
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.