Climate Change

Key Topic #1: Climate Change Projections

• Causes of climate change:
  • Buildup of greenhouse gases (GHGs) in the atmosphere.
  • Warming of the planet due to the greenhouse effect.
• Impacts of climate change:
  • Changing temperature and precipitation patterns.
  • Increases in ocean temperatures, sea level, and acidity.
  • Melting of glaciers and sea ice.
  • Changes in extreme weather events (frequency, intensity, duration).
  • Shifts in ecosystem characteristics (growing season length, flower blooms, bird migration).
• Greenhouse effect:
  • Natural process where certain gases in the atmosphere absorb energy, slowing/preventing heat loss to space, thus warming the Earth.
  • Necessary to support life but amplified by human activities.
• Key Greenhouse Gases:
  • Carbon Dioxide ($CO_2$):
    • Primary GHG, enters atmosphere through burning fossil fuels, solid waste, trees, and chemical reactions like cement manufacturing.
    • Absorbed/emitted naturally through the carbon cycle.
  • Methane ($CH_4$):
    • Produced by natural wetlands, agricultural activities, and fossil fuel extraction/transport.
  • Nitrous Oxide ($N_2O$):
    • Produced mainly through agricultural activities and natural biological processes; also from fossil fuel burning and industrial processes.
  • F-Gases:
    • Include chlorofluorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride.
    • Used in coolants, foaming agents, fire extinguishers, solvents, pesticides, and aerosol propellants.
  • Global Warming Potential (GWP):
    • Measure of climate impacts based on how long each GHG remains in the atmosphere and how strongly it absorbs energy.
  • Other Greenhouse Gases:
    • Ground-Level Ozone ($O_3$): Created by a chemical reaction between emissions of nitrogen oxides and volatile organic compounds in sunlight. It traps heat and is a pollutant that can cause respiratory problems and damage crops/ecosystems.
    • Water Vapor ($H_2O$): A key player in climate feedbacks due to its heat-trapping ability. Warmer air holds more moisture, amplifying warming.
  • Aerosols:
    • Microscopic solid or liquid particles suspended in the air, affecting climate by absorbing or reflecting sunlight.
    • Sources: Human activities (burning fossil fuels and biomass) and natural sources (volcanoes, marine plankton).
    • Reflecting aerosols (e.g., from volcanic eruptions) have a cooling effect, while absorbing aerosols (e.g., black carbon/soot) have a warming effect; targeted reductions in black carbon emissions can reduce global warming.
• Climate Feedbacks:
  • Natural processes that respond to global warming, offsetting (negative feedbacks) or further increasing (positive feedbacks) climate change.
  • Positive feedbacks:
    • Water vapor: Warmer temperatures increase evaporation and water vapor in the air, leading to further warming.
    • Melting of Arctic sea ice: Loss of ice exposes darker sea surface, which absorbs more sunlight and increases warming.
  • Clouds:
    • Have both warming and cooling effects.
    • Cool the planet by reflecting sunlight during the day.
    • Warm the planet by slowing heat escape to space, mostly at night.
    • Changes in coverage, altitude, and reflectivity of clouds can either amplify (positive feedback) or dampen (negative feedback) the original change. Net effect is likely positive.
• Climate Change Indicators: Snow and Ice
  • Snow and ice can easily change between solid and liquid states in response to relatively minor changes in temperature.
  • Rising global average temperature correlated with changes in weather patterns and frequency/intensity of extreme weather.
  • Observed changes:
    • Rising temperatures in the U.S. (especially North, West, and Alaska) and globally (nine of the top 10 warmest years on record have occurred since 1998).
    • Seasonal temperature increases, especially in winter and spring.
    • More frequent extreme temperature conditions (hot summer days/nights).
    • Heat waves (occurring more often, lasting longer, becoming more intense).
    • Increased total annual precipitation in the U.S. and worldwide, but with regional variations (e.g., less precipitation in the Southwest).
    • Heavy precipitation (more precipitation in intense, single-day events; increased abnormally high annual precipitation totals).
    • Increased tropical storm activity in the Atlantic Ocean, Caribbean, and Gulf of Mexico.
    • Changes in river flooding (increases in Northeast and Midwest, decreases in West).
    • Variable drought conditions, with specific trends varying by region.
    • Southwestern U.S. particularly vulnerable to drought due to temperature changes.
• Weather vs. Climate
  • Weather: State of the atmosphere at a specific time and place (temperature, precipitation, clouds, wind).
  • Climate: Long-term average of weather in a given place (temperature, precipitation, frequency/intensity of weather events).
• Impacts on Canada(Observed Trends - Temperature and Precipitation)
  • Economic Impacts:
    • Extreme events and natural disturbances cause economic losses (hundreds of millions to billions of dollars).
    • Impacts on buildings and infrastructure (increased maintenance, replacement costs, winter roads, coastal erosion, permafrost degradation).
    • Impacts on production, prices, and demand for goods and services (both positive and negative).
    • Costs related to public safety, health and welfare (vector-borne diseases, mental health, mold, financial hardship, culture, and traditional ways of life).
    • Hydrological changes in lakes and streams affect energy, tourism, recreation, freshwater fisheries, and transportation.
  • Population and Demographics Trends:
    • The elderly more vulnerable, proportion increasing.
    • Other vulnerable populations include children, Aboriginal people, people with pre-existing health conditions and the poor.
  • Temperature and Precipitation:
    • Canada has warmed by more than 1.3^\\circ C since 1948, twice the global average.
    • Greatest temperature increases in Yukon and Northwest Territories.
    • Winter and spring months have greater and more spatially variable temperature increases.
    • Winter temperatures in northwestern Canada increased more than 3 ^\\circ C between 1948 and 2003.
    • Mean precipitation across the country increasing by about 12 % since 1948, but varies by region and season.
    • Largest percentage increase in the high Arctic, southern Canada little change or even a decrease
  • Changes in Temperature and Precipitation Extremes (1950–2003):
    • Fewer extreme cold nights and days.
    • Fewer frost days.
    • More extreme warm nights and days.
    • More days with precipitation.
    • Decrease in mean amount of daily precipitation.
    • Decrease in maximum number of consecutive dry days.
    • Decrease in annual total snowfall in southern Canada, increase in the northern and northeastern Canada.
  • Other Observed Changes:
    • Reduction in the cryosphere (sea ice, snow cover, permafrost).
    • Arctic sea ice decreased by 8% since 1979.
    • Snow-cover duration decreased by about 20 days in the Arctic since 1950.
    • Permafrost temperatures increased (0.3 to 0.5 ^\\circ C per decade in the Canadian high Arctic and ranged from no change to almost 1 ^\\circ C per decade in the western Arctic).
    • Changes in the frequency of extreme temperature and precipitation events
    • Increase in thaw depth
    • Changes in temperature and precipitation led to changes in sea ice, snow cover, permafrost, evaporation and sea level.
    • Water levels in lakes across Canada have varied considerably over time, and recent trends toward lower levels in the upper Great Lakes, in association with higher temperatures, have been quite dramatic
    • Water levels in the Great Lakes are generally projected to continue to drop in the future
    • Global ocean levels have risen an estimated 0.17 m (range 0.12 -0.22 m)
  • Projections - Temperature and Precipitation
    • All of Canada is projected to warm during the next 80 years.
    • Regional differences in temperature projections are also illustrated in Figure 17, which shows historical and projected change in temperature for six citiesacross Canada
    • Greatest temperature increases will be in the high Arctic.
    • Warming will be greater in the central portions of the country than along the east and west coasts.
    • Warming is expected to be greatest during the winter months.
    • Decrease in the winter diurnal temperature range across the country
    • Rates of warming will be lower in the summer and fall.
    • The frequency of extreme warm summer temperatures (exceeding 30°C) is expected to increase across Canada.
    • Heat waves are projected to become more intense and more frequent.
    • Extreme cold days are projected to decline significantly.
    • Future precipitation is more difficult to project, and changes are generally of lower statistical significance
    • Annual total precipitation is projected to increase across the country during the current century.
• Other Projected Changes
  • Sea level will continue to rise, with global projections of 0.18 to 0.59 m by 2100
  • Changes in sea ice, storms and decreases in sea ice will all increase the rate of coastal erosion

Scenarios and Climate Models

• Representative Concentration Pathways (RCPs):
  • RCP8.5: high global emission scenario. Global average warming levels of 3.2 to 5.4^\\circ C by 2090.
  • RCP4.5: medium global emission scenario, includes measures to limit climate change. Global average warming levels of 1.7 to 3.2^\\circ C by 2090.
  • RCP2.6: low emission global scenario, requires strong mitigation actions. Global average warming levels of 0.9 to 2.3^\\circ C by 2090.
• Climate Models:
  • Simulate elements, including ocean temperatures, clouds, rainfall, and vegetation growth.
  • Global Climate Models (GCMs): Divide Earth into large grid cells (over 100 km).
  • Dynamically Downscaled Models (Regional Climate Models - RCMs): Simulate climate of a smaller region with finer resolution (10 to 50 km grid cells), relying on information provided by GCMs, using laws of physics.
  • Statistically Downscaled Models: Use statistical relationships between local and large-scale climate variables, then applied to projections from GCMs to simulate local climate.
  • Managing uncertainty in climate projections:
    • We can’t predict the exact amount of greenhouse gasses future human activity will produce.
    • We can’t perfectly model the Earth’s climate system.
    • Use of different scenarios or RCPs helps deal with the first issue.
    • For the second issue, multiple climate models, each constructed somewhat differently, are used.
    • The results from many climate models are grouped to create a “multi-model ensemble."
    • Then, percentiles (from statistics) are used to summarize the range of results from that ensemble.

Linking Climate and Inequality

• Climate Change and Inequality:
  • Climate change disproportionately affects the poorest countries and people due to higher exposure and vulnerability.
  • Poorest economies rely on climate-sensitive sectors (agriculture, forestry, fisheries).
  • Rising temperatures exacerbate disparities in access to clean water and food.
  • Poor populations lack insurance and access to basic health services, increasing vulnerability to shocks.
  • Developed economies contribute the most to GHG emissions.
• Mitigation Efforts
  • Mitigation policies may increase energy or food prices, affecting the poor most, who spend a higher share of income on these goods.
  • Mitigation efforts should be shared fairly to ensure they serve the broader objectives of development, poverty and inequality reduction, improvement of air quality, health, and so forth.
  • Financial transfers between countries can reduce the burden of mitigation for poorer countries and increase participation in mitigation efforts.
• Promoting adaptation and resilience
  • Adaptation policies must be put in place to decrease the exposure of the most vulnerable populations to climate change impacts.
  • Policies need to be tailored to ensure they do not impose undue financial constraints on those who have the fewest resources.
  • Creation of adaptation funds that would ensure technological transfers from rich countries to poorer ones.

Climate Change: World Health Organization

• Climate Change and Health:

  • Multiplies threats, undermining decades of health progress.
  • Increases weather/climate events which affect health directly/indirectly.
  • Impacts health workforce/infrastructure.
  • Degrades environmental/social determinants of physical/mental health.

• Climate Change Impacts on Health:

  • Climate risks appear faster and will become more severe sooner than previously expected, and it will be harder to adapt with increased global heating.

  • Poorest countries and small island developing states (SIDS) are the most affected.

  • Increase death, illness, extreme weather events, disruption of food systems, increases in zoonoses and food-, water- and vector-borne diseases, and mental health issues.

  • WHO projects 250 000 additional yearly deaths by the 2030s due to climate change impacts on diseases like malaria and coastal flooding.

  • Threatens to undo 50 years of progress in development, global health and poverty reduction.

  • To avert catastrophic health impacts and prevent millions of climate change-related deaths, the world must limit temperature rise to 1.5^\\circ C.

• WHO Response centers around 3 objectives

  • Promote actions that both reduce carbon emissions and improve health.
  • Build better, more climate-resilient and environmentally sustainable health systems.
  • Protect health from the wide range of impacts of climate change.