Causes of climate change

Best textbook-level introduction to the processes at play: Limits to Growth: the 30-Year Update (pdf)

Quick scroll-through visualization showing what causes global warming– oversimplified, but a good start

Mechanics: How Warming Occurs

  • Greenhouse gases trap heat in the atmosphere - if atmospheric carbon doubles, world temperatures raise by 10F Pearce, 4
  • The earth is getting warmer, and it's creating nasty positive feedback loops which could lead to tipping point events for rapid climate increase. For example: Sea ice is melting; ice is more reflective than water, so heat gets absorbed by the water more quickly than before; sea ice melts even faster
  • The primary cause of global warming is CO2 going into the atmosphere, specifically due to the burning of coal, natural gas, and petroleum. Victor
  • Nobody's exactly sure what will happen and when, but so far it's gotten worse more quickly than mainstream models predicted.
  • Current models suggest that CO2 emissions are increasing exponentially, and that CO2 causes logarithmic warming– thus, that we can expect roughly linear warming (assuming we don't reach a tipping point). This yields a warming rate of 1.1C every year globally, or 1.6C over land Muller, 49
  • Tipping point events could cause much faster global warming. For example: the Antarctic ice sheet loosens and slips into the sea, causing 100 feet of sea rise globally; freshwater from Greenland glaciers disrupts Gulf Stream current and thus currents throughout the Pacific Ocean; Methane is released from clathrates in melting permafrost or Arctic seabeds Muller, 51
  • "Owing to a combination of fossil fuel combustion and deforestation, the concentration of carbon dioxide in the air has risen by forty percent over the last two centuries, while the concentration of methane, an even more potent greenhouse gas, has doubled." Kolbert, 108
  • It's not just CO2– here are the major greenhouse gases:
Greenhouse gas Global Warming Potential (GWP) Remains in atmosphere Emitted from
Carbon dioxide (CO2) 1 (by definition of GWP) EPA-GWP 20-200 years to remove 65-80%, then hundreds of thousands of years Clark Fossil fuel combustion (coal, natural gas, oil), solid waste combustion, cement manufacturing EPA
Methane (CH4) 28-36 EPA-GWP 12 years Clark Natural gas combustion, production and transportation of coal, natural gas, and oil, livestock agriculture (cows, mostly), anaerobic decomposition of organic waste e.g. in landfills EPA
Nitrous oxide 265-298 EPA-GWP 114 years Clark Agricultural and industrial activities, combustion of fossil fuels and solid waste EPA
Halocarbons/CFCs 1000s-10,000s EPA-GWP Varies from less than a year to thousands of years. Here is a table. Freon (refrigerators), industrial processes EPA

Positive feedback loops

  • Global warming reduces the likelihood that we can count on forests and trees as permanent carbon sinks. Sequestration of carbon in forests fluctuates to the extent that some years forests can produce more carbon than they sequester Smil, 80. In the near future, Tropical forests’ carbon impacts will change in the near future mostly due to deforestation, but many other forests will be limited by water and soil nutrient availability, especially a lack of nitrogen. This is one of the effects of global warming. We will also have more carbon-releasing wildfires across these forests due to longer droughts from global warming. Smil, 82
  • Methane emissions from thawing peat bogs in Western Siberia are up to 100k tons/day, a greater warming effect than U.S. man-made emissions Pearce, 79
  • Stordalen mire: well-monitored permafrost peat bog in northern Sweden that is beginning to break up Pearce, 82
  • 1-10t tons of methane is currently held by clathrates Pearce, 92

Where the warming comes from

Note: this is super weird presentation of disparate facts. TODO: make this a section with charts

  • The world's highest-emission companies: Carbon Majors, 2017
  • The transport sector is responsible for 23% of global emissions Hawken, 136
  • Waste production grew tenfold in the last century and is expected to double again by 2025 (2017 stat) Hawken, 158
  • At least half of waste is generated outside households (industrial) Hawken, 160
  • 5-6% of the world's annual oil production is feedstock for plastic manufacturing Hawken, 168
  • 1/3 of plastic ends up in ecosystems, 5% is recycled; the rest is landfilled or burned Hawken, 169
  • Hot water is responsible for a quarter of residential energy use globally Hawken, 170

Politics: Why Warming Continues

Global political response

  • There is no decisive political action that can be taken regarding carbon emissions, because any that would actually work would also shut down the global economy.
  • Paris Agreement established the goal of limiting climate change to 1.5-2 degrees C above preindustrial levels and creates a process for emissions cuts. Sutter Obama administration released CPP as a concrete plan to meet these targets but it's currently held up in court (update expected Feb 2017)

We're not changing

  • Creeping normalcy and landscape amnesia make it easy for people to feel that the change we're experiencing is normal Diamond
  • The amount of carbon that can be burned between 2011 and 2049 to have a 50% chance of keeping global warming below 2 degrees celcius is 565 gigatons. Reserves already claimed by all fossil fuel companies for oil, gas, and coal amounts to 2,795 gigatons of carbon. Klein, 134

Continued effects even after we improve

  • The IPCC says we get 90 more years of climate change regardless of how much emission we stop. 2007: 385 PPM CO2. No way to avoid 450 PPM by midcentury according to Pew Center on Global Climate Change Begley
  • In order to have a 50% chance of keeping below the agreed-upon international target of no more than 2 degrees C of warming, all wealthy countries need to start cutting greenhouse gas emissions by 8-10% immediately (2015) Klein, 81

Planetary Impacts: How Much This Matters

Humans have drastically altered the planet

  • We are in the Anthropocene because: (1) human activity has transformed 1/3-1/2 of the land surface of the planet (2) most of the world's major rivers have been dammed or diverted (3) fertilizer plants produce more nitrogen than is fixed naturally by terrestrial ecosystems (4) fisheries remove more than 1/3 of the primary production of the ocean's coastal waters (5) humans use more than half the world's readily accessible freshwater runoff (6) humans have altered the composition of the atmosphere. To qualify as an epoch, we are leaving behind a global stratigraphic signature that will still be legible in millions of years. Kolbert, 108-109
  • "Since the start of the industrial revolution, humans have burned enough fossil fuels– coal, oil, and natural gas– to add some 365 billion metric tons of carbon into the atmosphere. Deforestation has contributed another 180 billion tons. Each year, we throw up another nine billion tons or so, an amount that's been increasing by as much as six percent annually. As a result of all this, the concentration of carbon dioxide in the air today– a little over four hundred parts per million– is higher than at any point in the last eight hundred thousand years. Quite probably it is higher than at any point in the last several million years. If current trends continue, CO2 concentrations will top five hundred parts per million, roughly double the levels they were in preindustrial days, but 2050. It is expected that such an increase will produce an eventual average global temperature rise of between three and a half and seven degrees Fahrenheit, and this will, in turn, trigger a variety of world-altering events, including the disappearance of most remaining glaciers, the inundation of low-lying islands and coastal cities, and the melting of the Arctic ice cap." Kolbert, 113
  • Roughly 50 million square miles of land are ice-free on the planet, and more than half of it has been directly transformed (cropland/cities/logging/etc.) by humans. 3/5 of the remaining land is natural but not untouched, e.g. pipelines or trails. The remaining less than 10 million square miles are high tundra, mountaintops, or desert. Kolbert, 176

Historical precedent: how drastic this is in the context of Earth's history

  • History of carbon in the atmosphere: 440b tons at the coldest part of the last ice age, 660b tons at the start of the Industrial Revolution (largely from the ocean). 2007: 880b tons. Current estimate for "safe" level of carbon: no more than 935b tons to get a 50% chance of staying below internationally recognized "dangerous" temperature rise. This is 55b tons more than already in the atmosphere in 2007. Current rate of emission: 8.2b tons/year emitted, ~60% stays in the atmosphere - so 4.4b tons/year. That puts us crossing the "safe" threshold around 2020. Pearce, 242
  • Most of the Ordovician period had a greenhouse climate (high CO2 levels in the air, high sea level, high temperature). Rapid drop in CO2 levels resulted in a big five extinction (according to current theory). Kolbert, 183

Effects of past global warmings

  • The end-Permian extinction (a big five extinction event) appears to have been triggered by a rapid rise in CO2/climate. Ocean temperatures rose ~18 degrees F, waters became more acidic and lost oxygen. 90% of species on earth became extinct over a period of 100-200k years. Kolbert, 183

[aggarwal]: https://www.sciencedirect.com/science/article/pii/S1040619013001917 "Aggarwal, Sonia and Harvey, Hal. 'Rethinking Energy Policy to Deliver a Clean Energy Future.' Energy Innovation, 2013."

[trabish-dynamic]: https://www.utilitydive.com/news/beyond-tou-is-more-dynamic-pricing-the-future-of-rate-design/447171/ "Trabish, Herman. 'Beyond ToU: Is more dynamic pricing the future of rate design?' Utility Dive, 2017."

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