Climate Change: The Science

Climate Change: The Science

EdX: UBCx Climate1x, Dr. Sara Harris, University of British Columbia

Course Goals

  • Describing how interactions among atmosphere, ocean, land, and life lead to climatic changes at all timescales. 
  • Evaluate the likely effect of historical human fossil emissions and land use changes on Earth’s energy balance and climate. 
  • Describe the direct observations of climate change in recent decades. 
  • Articulate the evidence attributing global warming in recent decades to human causes. 
  • Assess the utility - and limits - of climate models to predict global and regional climate change. 
  • Express an informed opinion on the scope and urgency of the efforts needed to both mitigate and adapt to climate change.
Books
State of the Science
  • Scientific understanding of Earth's climate system is one important factor that informs human decision-making. We build scientific understanding based on 
    • observations and measurements of the world around us, and 
    • models - representations of the climate system.
  • Observations:

    • Global average surface temperature over time, and that's gone up in the past century. Several different groups of scientists, using different approaches, all end up with essentially the same story. 


    • Atmospheric CO2, which has also gone up since measurements began in the late 1950s. 


    • Declining sea ice extent in the arctic as time goes on. 


    • Sea level rise. 

    • These are all quite different measurements, yet together they form a logical, coherent story about climate, based essentially on how physics and chemistry work. There's virtually zero argument about the trends in these measurements. 
    • Distribution of Summertime Temperature changes in the northern hemisphere over time. In this case, the average for comparison is average summer temperatures between 1951 and 1980. Temperature anomalies under the smooth curve in the grey area are considered to be within what we'd call normal for that time period. Over time, summertime temperatures have gradually shifted toward the warm end, with many more instances of what used to be considered extremely high temperatures. The probability of getting extreme warm events is greater than it used to be. And the probability of getting extreme cold events is lower than before.


    • Ice Core CO2 Concentration vs. Temperature. Air bubbles trapped in ice preserve samples of the atmosphere at times in the past, so we can directly measure things like CO2 concentrations back through time, which is about 800,000 years. We can reconstruct temperature records using a wide variety of approaches, including things like 
      • the chemistry of sediments in the deep ocean, 
      • the types of organisms that lived in the past, 
      • the chemistry of corals, 
      • the chemistry of ice, and 
      • lots of other approaches. 
    • The general relationship between temperature and CO2 overtime according to these data: When temperature is high, CO2 is also high.


 


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