Lecture 7_ Climate (1).pdf

Lecture 7: Climate Factors that affect climate change: ● Atmosphere ○ Greenhouse gases ● Biosphere ○ Photosynthesis and respiration ○ Oceanic biological pump ● Hydrosphere (and cryosphere) ○ Ocean circulation ○ Reflectivity (albedo) ● Geosphere ○ Tectonics ○ Catastrophic events (volcanism, meteorite...

Lecture 7: Climate Factors that affect climate change: ● Atmosphere ○ Greenhouse gases ● Biosphere ○ Photosynthesis and respiration ○ Oceanic biological pump ● Hydrosphere (and cryosphere) ○ Ocean circulation ○ Reflectivity (albedo) ● Geosphere ○ Tectonics ○ Catastrophic events (volcanism, meteorites) ● Changes in solar radiation ○ Sunspots ○ Earth’s orbit Climate forcing – drivers of climate: ● Greenhouse gases ○ CO2, methane, nitrous oxide ■ Burning of fossil fuels have increased these re-radiate heat in atmosphere, cause surface warming ● Aerosols ○ Dust, smoke, soot, sulfates ○ Burning of coal, volcanicn eruptions ○ Net effect is cooling Climate feedbacks – amplify or reduce effects of forcing: ● Positive = amplifying ● Negative = stabilizing ● Clouds ○ Reflect ~⅓ of incoming sunlight ● Precipitation ○ Warmer atmosphere → increased precipitation ○ But some regions drier ○ Effect on planet growth ● Forests ○ Trees remove CO2 from atmosphere (carbon sink) ● Ice albedo ○ Warmer → less ice ● Water vapour ○ Most abundant greenhouse gas ○ Warmer atmosphere → more water vapor Climate tipping point — abrupt shifts, irreversible: ● Ocean circulation ○ E.g. slowing of gulf stream → cooling in europe, but warming in North America ● Ice loss ○ Ice reflects light, land surface absorbs heat ○ Less ice → runaway heating ● Rapid release of methane ○ Thawing of permafrost will release methane ● Tipping points are not independent of one another! Other influences on climate: ● Oceanic biological pump ○ Photosynthesis uses CO2 + more dust during glacial period ■ → more nutrients ■ → stronger biological pump ■ → drawdown of CO2 ■ → further cooling Peatlands: carbon storage Evidence for warming climate: ● CO2 increase ● Temperature increase ● Sea-surface temperature increase ● Sea-level rise (1997-2023: 97mm) ● Loss of sea ice and ice sheets ● Retreat of glaciers ● More weather-realted disasters Effects of Canada: ● Snow fall will increase ● Erosion ○ Loss of sea ice causes more wave action at shor ● Ice roads ○ Costly all-weather roads may need to be built to support mines and communities ● Fire — wldfires below the tree line ○ Threaten infrastructure, remote microwave towers ● Melting permafrost — threaten structures ○ E.g. roads, runways, pipelines, fuel storage Climate engineering: ● Adjusting climate by ○ Increasing albedo ○ Removing CO2 Intergovernmental panel on climate change (IPCC) report 2023: ● IPCC established in 1988 by the UN ● Provides assessments and recommendations about climate change to policy makers ● Sixth report completed in march 2023 ● The graph summarizes: ○ The cenozoic climate ○ The recent ice ages ○ The human induced change ○ Predictions for the future climate