Global Warming The Enhanced Greenhouse Effect The Greenhouse

Global Warming: The Enhanced Greenhouse Effect § The Greenhouse Effect keeps our planet about 60 F warmer than it otherwise would be. Life as we know it depends upon this effect. Greenhouse gases (primarily water vapor and carbon dioxide) absorb/reemit IR radiation. § Enhanced Greenhouse Effect is “Global Warming” – Too much of a “good” thing – Anthropogenic (human-induced) § CO 2: correlates well with temp. § Methane § CFCs – low concentrations, but efficient IR absorbers very

Historical Temperatures vs. Historical CO 2 Levels For the 800, 000 years we have records, average global CO 2 levels fluctuated between about 170 ppm and 280 ppm. Once humans started to burn fossil fuels in the industrial era, things changed rapidly. Only in the industrial era has the number risen above 300 ppm. The concentration first crept above 400 ppm in 2013, and continues to climb. • Proxies: how do we get the data? • Milankovitch cycle (orbital changes) Data from Parrenin et al. 2013; Snyder et al. 2016; Bereiter et al. 2015. Image: Ben Henley and Nerilie Abram/The Conversation

https: //weatherdem. wordpress. com/2012/08/14/july-2012 -concentrations-394 -49 ppm/

http: //www. globalchange. gov/browse/multimedia/earths-temperature-variations

Methane: another player Methane data from NOAA, Temperature data source: NASA https: //earthobservatory. nasa. gov/images/87681/a -global-view-of-methane

Effect of Ocean Temperatures (PDO)

NOAA National Centers for Environmental Information, State of the Climate: Global Climate Report for October 2019, published online November 2019, retrieved on November 22, 2019 from https: //www. n cdc. noaa. gov/sotc/ global/201910/supp lemental/page-1.

Global Decadal Temperatures Global temperatures continue to climb. The 2010 s are warmer than the 2000 s

Sea Ice Change It’s really about albedo http: //www. chron. com/news/science-environment/article/Video-NASA-timelapse-footage-shows-Arctic-Sea-10424673. php

NASA Releases Time-Lapse Of the Disappearing Arctic Polar Ice

Climate Change: Some Uncertainties § Cloud cover: Should increase as temperature and condensation nuclei (pollution) increase, but type of cloud has an effect on surface temperature. Some cause cooling, some cause warming. Which type will increase more? Climate models still struggle with cloud prediction. § Speed of Sea Level Rise: Expected to rise as snow/ice melts, and as water warms (and expands), and is happening now, but some regions will see increased snowfall if planet warms, offsetting a little, but not much at all of the sea level rise – – – Recent dramatic cooling of top 2, 500 ft ocean layer? ? Not! More recent work on this ocean “cooling” Island nations especially concerned § Ocean Currents: Infusion of fresh water alters density, disrupts currents; local climate changes (warming and cooling) § Climate change: Gradual or Rapid? – “slipping” glaciers lubricated by meltwater

Sea Level Change It’s mostly about ice sitting on land § Thermal Expansion § Icecaps and Glaciers (Greenland)

GRACE (Gravity Recovery and Climate Experiment) data

Sea Level Change Not consistent around the world, but overall sea level is rising!

Climate Change: Other Uncertainties § Political Forces – Will countries play by the rules after ratifying a treaty? (I doubt it) – Should developed countries curtail their emissions and let developing nations continue until their emissions become “substantial? ” – Should developing nations be denied the chance the U. S. and other developed nations had? § No, it’s only fair. We can’t stifle their development § Yes, we know more today about what we’re doing to the planet – Then, should developed nations cover the increased cost developing nations will incur to meet stricter environmental guidelines? After all, we screwed it up in the first place. – What is FAIR?

The cartoon on the right makes a good point—what does it mean to you? What would you say about the two cartoons below?

Paris Accord: U. S. is Out

And Finally…. . Thinking about what it was like to be very dependent upon others for our energy needs and recognizing how things have changed, are we better off now? § “And finally, most important of all, basing an economy on a commodity that [in my opinion] is controlled by the most backward, unstable, and violent countries in the world is madness. ” (2006, but still relevant) - Craig Bohren, in USA Today § Now we have fracking. So, is cheap energy and the potential for energy independence necessarily a good thing?

What Should We Do? Geoengineering? Any possible problems with that?

Final Points § “We’re inching ever closer to committing to the melting of the West Antarctic and Greenland ice sheets, which will guarantee 20 feet of sea level rise. We don’t know where the ice sheet collapse tipping point is, but we are dangerously close. ” – Dr. Michael Mann, Penn State – Rolling Stone, December 2017 § READ CHAPTER 18, it’s all important