Global Warming What is it? What’s causing it? Lake Powell, Colorado River

CO2: one of the main heat-trapping gases CO2: one of the main heat-trapping gases. Its concentration in the atmosphere, past 250 yrs. Past 10,000 yrs NOTE: This is an old graph. The CO2 concentration passed 400 parts-per-million in 2013.

It’s getting warmer NASA IPCC Hottest years: 2016 2015 2014 2010 2005 1998 Hottest decade: 2001-2010 IPCC

Glacier nat park, Montanna-1 Montana: melting 1850: 150 named glaciers. 2007: 26. 2030: 0 expected

Alaska: melting

Austria: melting

HIMALAYAS: MELTING. Mt. Everes (left), 1921 and 2007

Arctic: melting. 1979 and 2003 Expected to be ice-free in summer by 2030. Reflectivity feedback could have serious consequences for Greenland.

Greenland surface melt extent. Complete melting: 24 ft sea-level rise.

The West Antarctic ice sheet is melting Would raise sea levels 16 feet Would take a few centuries May be already unstoppable

• To see what this means, let’s turn to the past. • 800,000 years of climate history. • The “Pleistocene”: 2.5 Mya – today. • CO2 was ~180 to 300 ppm. present interglacial Temperature (red) CO2 (blue)

Today’s CO2 concentration: above 400 ppm! CO2 (blue) Temperature (red)

To see what 400 ppm means … … we must go back before the ice ages (2.5 Mya to today):

The last time CO2 concentration was ~ 400 ppm: • Pliocene era, 5 Mya - 2.5 Mya. Poles much warmer, tropics slightly warmer. Average temps were 6 deg F warmer. Sea levels 70 feet higher.

Will the CO2 spike be the icon of a new geological age? Many geologists have already named it: The Anthropocene

Is this what you want for your grandchildren? It’s a moral issue.

physics.uark.edu/hobson Thank you THANK YOU! ART HOBSON ahobson@uark.edu Website: physics.uark.edu/hobson We’re all in this together!