climate change

temperature of planet Earth over time

graph where the 0 line represents the average temperature from 1960-1990, used to compare temperatures to what we think it was in the past

natural forcing mechanisms for climate change

solar output (luminosity), continental drift and climate, thermohaline circulation, distance/angles between the Earth and sun, and changes in atmospheric composition

solar output (luminosity)

11 and 22-year cycles of fluctuating irradiance; 40-50 years of reliable messurement suggests a potential increase of approx. 0.09 watts during periods of maximum luminosity (compared to 0.4 watts from GHGs)

continental drift and climate

ocean currents change in response to continental movement, changing how the ocean transports warm and cold water; when equatorial ocean currents circulate the earth is warmer, and when they are blocked, polar temperatures drop

deep ocean/thermohaline circulation

warming after the last ice age caused large amount of freshwater to be released into the ocean, slowing the ocean circulation which causes strong cooling over the North Atlantic for 600-1000 years (the young dryas period)

distance/angles between the Earth and sun

distance and angle between the Earth and sun has varied, the sun changes in energy output and the Earth’s orbit brings it closer to and farther away from the sun in a predictable cycle

Milankovitch cycles

changes the duration and intensity of sunlight reaching the Earth, 3 distinct cycles in how the Earth rotates around the sun, variation in these 3 cycles are believed to be the cause of Earth’s ice ages (glacials)

changes in atmospheric composition

the strongest candidate to explain overall patterns in Earth climate that can account for the changes of the last 100-200 years

understanding the 0.8℃ warming of the last 150yrs

not the warmest period ever in Earth’s history, but unique in that it cannot be explained by any natural forcing mechanisms as we currently understand them

causes of global climate changes

greenhouse gases explain warming trends, allows the penetration of visible and traps infrared radiation, a significant portion of which stays trapped on Earth and warms the atmosphere

radiative forcing

the imbalance in the Earth’s energy budget that results when the amount of energy radiated to outer space being changed through either natural or human influences

positive radiative forcing

results in warming; factors include GHGs, CFCs, nitrous oxide, tropospheric ozone, black carbon, sun, volcanic aerosols

negative radiative forcing

results in cooling, natural mechanism can cool the climate; factors include stratospheric ozone, reflective aerosols, soil dust, cloud changes, changes in land use, volcanic aerosols

cooling the atmosphere

some pollutants and atmospheric aerosols can cool the atmosphere as they reflect sunlight back into space, preventing the transmission of radiation into the atmosphere

causes of the enhanced greenhouse effect

the amount of gas emitted and properties of the gas

average residence time

the length of time gas resides in the atmosphere

global warming potential

how much given mass of greenhouse gas contributed to global warming over a period of time compared to the same mass of carbon dioxide

causes of the enhanced greenhouse effect

average residence time and global warming potential

average residence time

the length of time gas resides in the atmosphere

global warming potential

how much given mass of greenhouse gas contributed to global warming over a period of time compared to the same mass of carbon dioxide

5 significant pools in the carbon cycle

atmosphere, forests and soils, surface ocean, deep ocean, fossil fuel

carbon fluxes

photosynthesis/respiration, changing land use (deforestation, forest regrowth), surface ocean flux (oxygen from the atmosphere gets dissolved), flux to the deep ocean (carbon from the surface moves to the deep ocean), fossil fuel

terrestrial photosynthesis

fossil fuels account for more than 2x the carbon currently stored in forests and soils, not able to absorb all the fossil fuels as even if we could double forested areas to absorb 4280 GT, we would still have excess CO2 to dispose of eventually

increased ocean uptake

even if the oceans could absorb more CO2, this option is limited by the rate at which it moves out of the shallow oceans into marine organisms and deep oceans

International Panel on Climate Change (IPCC)

the leading international body for the assessment of climate change, est. 1988 with the purpose of providing a clear scientific view on the current state of knowledge in climate change and its potential environmental and socio-economic impacts

1.5℃ global warming

the increase in the Earth’s average temperature from the baseline average temperature (1960-90), enough heat and energy to tip many important natural systems past a dangerous turning point

potential impacts of going from 1.5℃-2℃

billions more people will experience severe heatwaves, seas rise another 10cm, climate-related risks and poverty, coral reefs could decline up to 99%, the global fishery could decline, impacts on developing economies

changes in the Arctic and Antarctica

polar amplification is exacerbated by feedback mechanisms: the release of methane and CO2 stored in permafrost, and melting of ice and snow will raise sea levels and decrease the salinity of the ocean

impact on polar bear populations

they rely on ice to help it hunt further into the ocean, and the melting causes more polar bears to be on coastlines and unstable hunting

ecological effects

affects every species on earth, some will expand their range and thrive; the greatest risks are polar seas, coral reefs, mountain ecosystems, coastal wetlands, and tundra

dealing with global climate change

focus must be CO2, two methods are mitigation and adaptation

mitigation

moderating/postponing global climate change, i.e. buying time: reducing CO2 emissions through developing fuel alternatives and increasing energy efficiency; planting and maintaining trees to increase photosynthesis

adaptation

responding to changes, implies that climate change is unavoidable

geo-engineering and climate engineering

large-scale engineering and manipulation of the planetary environment to combat/counteract anthropogenic changes in atmospheric chemistry

CO2 management

separate and capture, sequester from the atmosphere, artificial ocean upwelling, ocean iron fertilization, ocean alkalinization

solar radiation management

reduce the amount of solar radiation reaching the earth, i.e. spraying millions of tonnes of reflective particles of sulphur dioxide, mimics volcanic eruptions