# AP Environmental Science/Climate Change
## Past Climate Change

Scientists determine what temperatures were present in the past through a few techniques:
* Tree rings: If the tree ring is wide, then it means the climate was warm and rainy; If the tree ring is narrow, then it means the climate was cold and drought-ful.
* Plankton in ocean sediments.
* Small bubbles of ancient atmospheric gas found in ice cores taken out from ancient glaciers.
* Temp. measurements are taken from boreholes at different depths.
* Pollen from the bottoms of lakes.
* Historical Records (writings)

## Greenhouse Gas Sources

* CO$_2$ (Carbon Dioxide): Aerobic Respiration, Aerobic Decomposition, Naturally-Occuring Fires (combustion), Fossil Feuls, Deforestation.
* CH4 (Methane): Anaerobic Respiration, Increase in anaerobic decomposition, belching of cows, fossil feuls, rice production.
* N$_2$O (Nitrous Oxide): Denitrification, Fertilizing, Hot Motors, Deforestation.

## Climate Forcing

A climate forcing is an imposed perturbation of the planet's energy balance. All climate forcings are natural/anthropogenic and positive/negative. The climate of the Earth respond to these forcings:
| Natural | Anthropogenic |
| Brighter sun (+) | Greenhouse gases - CO$_2$, chloroflourocarbons, methane (+) |
| Volcanic blast (-) | Black carbon/soot, aersolos (+) |
| | Sulfur aerosols (-) |

### Natural vs. Human Activity: Contributors to Global Warming
#### NATURAL

* Volcanic eruptions that spew out aerosols which caused the Earth to cool.
* Variations in sunlight (tiny wobbles in the Earth's orbit can determine where the sunlight is reached upon Earth)

#### Man Made

* Burning of fossil fuels (release methane, nitrous oxide)
* Deforestation (removing of trees, more carbon dioxide and methane in the atmosphere)
* Raising cattle (cows: belching and farts increase emissions of methane)
* Fertilizing and hot motors from cars increase nitrous oxide.
* Rice production increases methane.

## Aerosols

Aerosols are tiny particles scattered out and about in the air. They have the ability to affect global climate (see Mt. Pinatubo). Effects of aerosols include:
* reflect/absorb sun-rays; warmer
* Soot builds up on snow, lowers the albedo.
* Aerosols seed the clouds, causing a change in precipitation. This greatly affects clouds/water vapor, causing an increase and then decrease (precipitation).
* Atmospheric circulations can be changed; the atmosphere is a shared resource (see "tragedy of the commons").
It is complicated to measure aerosols since they are distributed throughout the atmosphere (complex) and the relationship between the ocean and atmosphere (complex).

## Greenhouse Gas Emitters

| Countries | 2004 | 2014 |
| U.S. | 22 | 15 |
| China | 14 | 30 |
| EU | 13 | 9 |
| Russia | 6 | 5 |
| Japan | 5 | 4 |
| India | 4 | 7 |
China and India increased their coal-powered electricity production.

## Evidence of Global Warming/Harms of Global Warming
### Evidence of Global Warming

* Since 1900, the average global temperature has risen 1.1 F.
* Over the past 50 years, Arctic temperature has risen 2 times faster than the rest of the world.
* 4-8 inches of sea-level rise has been recorded in the past century due to the expansion of the seawater from increasing temperatures and runoffs from melting ice (glaciers).
* Glaciers and ice are melting fast.
* CO$_2$ and CH$_4$ are released from melting of permafrost in Alaska and Russia.
* Ocean Acidification increased CO$_2$ levels (it is worth mentioning that oceans do HELP in the control of global warming: they absorb heat and form carbonate ocean sediments--but when the temperature increases in the ocean, then the ocean heats up some of its dissolved carbon dioxides, which [this CO$_2$] could be released into the atmosphere. Also when too much CO$_2$ is found in the ocean, this CO$_2$ increases the ocean's acidity, which lessens the ocean's ability to remove CO$_2$ from the troposphere).

### Harms of Global Warming

* Melting of glacial ice can increase sea levels, which pose as threats (flooding) to coastal cities such as New Orleans and Miami and it poses as threats to islands such as the Maldives and the Pacific Islands.
* Global Warming will lead to long periods of drought and long periods of rain (flooding) in some areas of the world. This will happen due to the altering of regular patterns of precipitation by changes made into the distribution of water made by the water cycle. Long periods of drought can occur in places such as Africa and Asia, which will cause crops/people to die and an add-on to the refugee crisis already existing in the world today (more environmental refugees). In areas with excessive rain, flooding will occur and many people will die by drowning (and more environmental refugees). Also, global warming could increase the already-destructive intensity of hurricanes by heating the ocean.
* Animals could go to extinction due to the rise of temperature and disease-carrying pests would thrive. Polar bears are a great example of this, as the ice on which they depend on for shelter would be gone because they've been melted. On the other hand, mosquitoes who have the potential of carrying terrible diseases such as malaria and yellow fever, can live and thrive on the increased temperatures.

### How were we saved from a mini-ice age (glacial period)?

Our ancestors actually DID indeed save us from a mini-ice age! This is what they did:
* An increase in carbon dioxide and methane began about 10,000 years ago when they started to clear and burn small plots of forest (deforestation).
* Larger areas of forests were deforested, burning areas of grassland to attract animals (game) and grow berries + cattle (cow), through their belches and farts, emit a lot of methane (livestock).
* 5k years back: flooding of lowlands to grow rice (rice production).
Sounds nice, right? In fact, it does! Until we realize that we are putting our descendants at risk of a warmer Earth (not good). More deforestation, burning of fossil fuels and agriculture and population will lead to this.

## Albedo

Albedo - The fraction of solar energy (shortwave radiation) reflected from the Earth back into space.
* Ice has a high albedo (especially with snow on top)
* Average Earth's albedo: .3
* Measure of the reflectivity of the Earth's surface.

## Global Warming control on CC

* Cut the burning of fossil fuels, especially coal, which release carbon dioxide and methane into the atmosphere.
* Cut down on reforestation which produces CO$_2$ and N$_2$O and plant trees (massive reforestation) in order to reduce CO$_2$ levels.
* Raise fewer cattle, such as cows, or use animal feeds that reduce the emissions of methane. Stop the production of dairy products/beef, as they increase the methane in the atmosphere.
* Shift to renewable resources, such as wind, oxygen, and sunlight.
* Improve energy efficiency
** Especially solar, wind, geothermal
* Use sustainable agriculture (Remove CO$_2$ from smokestack)
* Reduce methane/black soot
** Trap methane from escaping from landfills
* Shift from coal to natural gas

## Global Change Pt. 2

* Kyoto Protocol (1997) - Cut greenhouse gas emissions by at least 5% below 1990 levels by 2012.
* Paris Agreement (2015) - Voluntary-reduce greenhouse gas emissions to a cap of 2 degrees C above pre-industrial levels or no more than 15 degrees C above current increase (no more than .5%).
* IPCC - Intergovernmental Panel on CC established by the UN and NMO in 1988.
* VA Power - 12% of VA energy must be by renewable resources by 2022.