human causes of climate change Flashcards
describe the changes to the climate over geological time
whilst there have been changes in the climate over geological time, the changes experienced over the last 200-300 years have been significant.
describe CO2 levels throughout geological time
throughout geological time CO2 levels have remained constant, being between 260-280 ppm (parts per million) over the last 10,000 years. however, today these levels have risen to 420 ppm. the reason these levels have increased so dramatically is mainly to do with human activities
what does flooding of rice fields cause
flooding off a rice field cuts off the oxygen supply from the atmosphere to the soil, resulting in a process called anaerobic fermentation.
describe anaerobic fermentation
this is where the organic (living) matter in the soil starts to break down due to a lack of oxygen and is decomposed by a microorganism, methanogen archaea
what product is produced from archaea
as archaea break down the organic matter, methane is the waste by-product produced from this process.
how is the gas released from soil
the CH4 gas is released from the submerged soils to the atmosphere through the roots and stem of the rice plants (hallow like structure) or it is released directly from the field into the atmosphere when the water evaporates
how much rice is produced each year
507 million metric tonnes of rice produced in 2020-2021
which countries consume the most rice
rice is a staple food in many countries with China consuming more than any other country (155 million metric tonnes in 2021-2022) followed by India (104 million metric tonnes in 2021-2022)
how much CH4 (methane) does rice cultivation produce
50-100 million tonnes of CH4 per annum
is CH4 more potent then CO2
methane is 25 times more potent as a greenhouse gas then CO2
what is the largest contributor to agriculture greenhouse gases
livestock
how much emissions does livestock produce
it creates approximately 29% of global CH4 emissions. 9% of CO2 emissions (from respiration, land clearing, processing and transportation) and 65% of nitrous oxide emissions (from manure)
how many emissions does livestock account for in Australia
in Australia, direct livestock emissions account for almost 70% of total national greenhouse gas emissions
where does methane come from
methane is created from ruminant livestock, such as cows, sheep and goats, which are domesticated animals
what is cud
regurgitated food that is continually chewed again
what is the CH4 output dependent on
on the number of livestock that we have on earth at any given time.
how many cows and sheep are there in 2022
1 billion cows and 1.2 billion sheep
CH4 produced by each cow, sheep and pig
sheep=8kg of CH4
cow=60-120 kg of CH4
pig=1.5 kg of CH4
how much of the national CH4 productioncis produced from livestock
66%
how is methane produced from animals
from these ruminant livestock during their digestive process, which is called enteric fermentation
where do methanogen archaea live
the methanogen archaea also live in the cow’s (and their ruminant animals) rumen, which is their first stomach and is responsible for breaking down the grass, making it inedible
what is the by-product of this fermentation?
the by-product or waste product from eh archaea breaking down the cellulose in the grass is CH4 which is released through the mouth by belching or when the grass is regurgitated and chewed again
what does this methane cause
this CH4 enters the atmosphere and increases the layer of greenhouse gases, trapping more terrestrial radiation- ultimately impacts on the heat budget and the enhanced greenhouse effect
