Lecture 10 - Greenhouse Gases and Climate Change

ice age

cycles between glacial and interglacial periods

EPICA and Vostok

ice age estimations from ice cores

ice volume

ice age estimates from sediment cores

who were the 4 pioneers of climate prediction?

Tyndall, Arrhenius, Bjerknes and RIchardson (also Foote but she was not acknowledged at the time)

Tyndall discoveries

assayed how different gases absorbed radiation by measuring effects of different gases on temperature like water vapour, CO2, etc

• also discussed the greenhouse effect of water vapour

Foote discoveries

measured how different gases absorbed radiation mostly regarding solar radiation discussing the greenhouse effect of H2O and CO2 and potential to lead to climate change

Arrhenius discoveries

calculated the overall effects of CO2 as a greenhouse gas

what was Arrhenius’ prediciton?

that doubling atmospheric CO2 should cause global temperature to increase by 4C

Arrhenius’ conclusions

• alternating glacial and interglacial periods were due to CO2 fluctuations in the atmosphere and the more fluctuations there were the more absorption there was

• increased coal burning by humans was fending off the next iceage

what idea led to rejection of Arrhenius’ findings?

favour of Milankovich cycles

Bjerknes’ discoveries

wrote the primitive equations for a model of weather including air movements, temperature and water content

how did Richardson use Bjerknes’ equations?

used to calculate the first numerical weather prediction, predicting weather for 6hrs and it took him 6 weeks to do so

ENIAC

first weather prediction computer that predicted 24hrs of weather in 24hrs

why is weather not predictable?

because of the chaotic nature that limits accuracy of estimation by computing systems

how is climate predictable?

because it is the aggregated statistics of weather (acts as some kind of long-term average of weather effects)

how do we predict climate?

apply a backward prediction mechanism by developing a climate model and getting a set of predictions then comparing those with what actually happened to evaluate how good the models actually are

intergovernmental panel on climate change (IPCC)

group of experts in climate literature that got together and dictated what’s accurate and what’s not to establish what is a firm, moderate or unique projection in order to avert alarmist projections by independent scientists

IPCC protocol

they don’t conduct research but provide protocols and reviews to assess to see which results are most robust, consistent and best supported by data and neutral with respect to policy (says what happens but not what we should do abt it)

greenhouse effects

radiation trapping, some infrared radiation passes through the atmosphere but most is absorbed (1/2) and re-emitted in all directions by greenhouse gases warming the Earth’s surface and the lower atmosphere

albedo

reflection of radiation back out into space

solar radiation

powers the climate system and some of it is reflected by the earth and the atmosphere

CO2 measurements in Hawaii (Keeling)

atmospheric concentration drops in July taken up by photosynthesis during northern summer and then it recovers during northern winter

what is the overall trend of atmospheric CO2 concentration?

it is upward

what country is the biggest emitter of greenhouse gases?

China

what contries are the biggest emitter per capita (per person)?

Canada and australia because they have smaller population sized but emissions comparable to countries with way bigger population sizes

greenhouse gases ranking based on relative effects per molecule

H20 (0.5), CO2 (1.0), CH4 (30), N2O (200), chlorofluorocarbons (30k)

CH4 (methane)

produced by anaerobic organic decomposition and grazing

N2O

produced by denitrification and combustion

chlorofluorocarbons

produced by refrigerants and spray can propellants

sea levels projection

they are predicted to rise indicating increasing in ice thinning due to warming

albedo breakdown

fresh snow reflect (75%), crops (20%, forest (10%), water (5%)

effect of climate warming on snow and water reflects?

prior cooling was associated with uplift of mountain ranges and creation of new snowy regions but now dramatic decrease in this regard because of warming