Climate change (Class of 2019): Introduction

• [x] What is your climate like? (Kids' Crossing) by University Corporation for Atmospheric Research, USA
• What is climate? ... Three layers of the concept of climate.
  • 1. Natural environment surrounding human settlements, with emphasis on conditions of the atmosphere near the ground -- e.g. hot/cold, wet/dry . (風土 ja:hû-do, zh:feng-tu, literally "wind and soil".)
  • 2. State of near-ground atmosphere, which can be expressed by multi-decadal (typically 30-year) statistics of physical (meteorological) variables. e.g. air temperature, precipitation (rainfall and snowfall). Note: not only the average but variabilities and extremes are relevant.
  • 3. State of the "climate system" (to be discussed shortly).
• Weather and climate (meaning No. 2): a matter of time scales
  • weather (ja: 天気 tenki; 気象 kisyô) ... hours to days.
  • (short-term climate?) (ja: 天候 tenkô) ... weeks to years (regular seasonal variation sorted out)
  • climate (ja: 気候 kikô) ... decades, centuries or longer.
  • Note: Inter-annual variability (of tenkô) exist within any one state of climate (kikô). In English, "climate prediction" usually means prediction of inter-annual variation. In Japanese, this activity is usually called "季節 予報 kisetu yohô literally "seasonal prediction (of something)".
• [x] Global Average Surface Temperature Anomalies by Japan Meteorological Agency (気象庁 Kisyôtyô)
  • (Japanese version is [here])
• Climate change (ja: 気候 変化 kikô henka; 気候 変動 kikô hendô)
  • The state of climate can change, in various time scales.
  • Climate may change because of external forcing, or it may change spontaneously.
  • To understand changes of climate (even if meaning No. 2), we need the concept of "climate system".
• Overview of the "climate system"
  • Components: atmosphere, ocean, ice and snow, "land surface"
    • [A schematic diagram (1975, GARP Publication Series)]
  • Stock and flow of mass (mainly of H₂O) and of energy
  • Feedbacks
• Global environmental issues (地球 環境 問題 tikyû kankyô mondai) as interaction between natural environment and human society
  • Human society is embedded in natural environment. But it is rather an autonomous system. So we think of interactions between natural environment and human society.
  • Natural environment poses constraints to human society (though it does not completely determine it.)
  • When human population was small, human society did not modify natural environment so much. The interaction is almost in one-direction.
  • As human population and per-capita activity grow, humans modify natural environment, so mofify the constraints to human society. When the modification is unfavorable to humans, it is recognized as environmental problems.
  • Agriculture and deforestation caused regional environmental problems. Migration may be solution.
  • Industrialization (popular use of fossil fuel) caused global environmental problems. We cannot escape from the global earth.
  • Figures: see [Earth system(s) and environmental problem(s)] (where "natural environment" is divided into "atmosphere + hydrosphere" and "ecosystem")
• "Climate change" as a natural process
  • Internal (spontaneous) change
  • Change due to natural forcing
  • Change due to anthropogenic (=caused by humans) forcing
• Can climate be changed? ... The following 3 questions are very different from each other.
  • This issue was not mentioned in the lecture of 2019-04-11. It will be discussed in some other day.
  • 1. Can climate change (in a time scale of a century, e.g. a few generations of human beings)?
  • 2. Can human activities change climate significantly?
  • 3. Can humans change climate as they like?
• Anthropogenic climate change as a global environmental issue