Geography - Weather & Climate (EQ2) Flashcards
What is global climate change?
Variation in the global climate or climatic patterns in the long term, e.g. major changes in temperature, precipitation, wind patterns.
What is global warming and its causes?
Increase in global temperatures over a long period of time.
Climate change can be due to natural variability of climate (natural causes) or anthropogenic factors (human activities).
What are the natural causes of climate change?
Changes in the Earth’s orbit and angle of tilt, sunspots, global dimming.
How does changes in the Earth’s orbit and angle of tilt cause climate change?
Orbit shape:
Over time (orbit changes every 100,000 years), the pull of gravity from Jupiter and Saturn causes the shape of Earth’s orbit to vary from nearly circular to slightly elliptical
Elliptical → Earth travels in an oval shape → more radiation reaches Earth when it is closest to the sun
It affects seasonal temperature.
Tilt:
Earth’s axis varies back and forth between 21.5 and 24.5 degrees (41,000 year cycle)
Tilt decrease → Hemispheres lean further away from the sun → leads to warmer winters and cooler summers; enables build up of large ice sheets in higher altitudes cooling the earth
How do sunspots cause climate change?
Areas that appear dark on the surface of the Sun; have lower temperature
Higher amounts of solar radiation from the sun → more sunspots → areas surrounding the sunspots radiate more energy → sunspot energies lead to more solar flares; burst of energy from the sun → more radiation given off → a lot more shortwave radiation → global temperatures go up during solar maximum
How does global dimming cause climate change?
→ Large-scale volcanic activity (releases large volumes of CO2, sulphur dioxide, dust and ash into the atmosphere; the heat released is small-scale so it doesn’t affect temperature)
Layer of ash (sulphur-based particles, dust and ash) spread around the lower atmospheric area of the earth → they absorb and reflect solar energy back into space → less shortwave radiation (offsets the greenhouse effect, lowering temperature)
Over time, the particles grow large enough and fall down to earth, and the effect subsides (can take months to years)
