Climate Change

• Ice cores are used to measure the amount of CO2 in the atmosphere over time. Glacial ice contains dust, air bubbles or isotopes of oxygen that can be used to interpret the past climate at the time the snow fell and formed the ice. Temporally these go far back in time (800,000)
• Fossil pollen can be analysed to reconstruct long run changes in vegetation and climate (240 million years). They can show what vegetation was growing in the time and assumptions about the climate can be made from the vegetation.
• Ocean and lake sediments consist of biological and other materials that were produced in the lake/ocean or that washed in from nearby land. They are preserved due to the lack of oxygen and can be used to interpret past climate. (5 million years)
• Tree ring dating or dendrochronology scientific dating based on the growth rings of trees and contain annual records of climate conditions. (thousands of years)
• Photographic evidence can also give insights into climate (Frost fair on the Thames in 1677)
• Advance or retreat of glaciers is a clear response to variations in climate
• Orbital eccentricity, obliquity and precession of Earth's Axis and three cycles collectively known as Milankovitch Cycles.
• The Milankovitch cycles create alterations in the seasonality of solar radiation reaching the earth's surface and these times of increased or decreased solar radiation directly influence the earth's climate system.
• Eccentricity is how Earth's orbit shifts from being elliptical to being nearly circular the back to elliptical. The more elliptical the orbit is, the greater the variation in solar energy.
• As Earth rotates on its polar axis, it wobbles and the Earth is closer to the sun in January (perihelion) and further away in July (aphelion).
• Changes in the tilt (obliquity) of the Earth over a 41,000 year period. During the 41,000 year cycle the tilt can deviate from approximately 22.5 degrees to 24.5 degrees. When the tilt is small there is less variation between the summer and winter seasons. Winters tend to be milder and summers cooler
• Volcanic eruptions cause short term climatic change. One of the coldest years in the last two centuries occurred the year following the Tambora volcanic eruption in 1815. Sulfur dioxide was ejected into the atmosphere and reacted with water vapour in the stratosphere to form a dense optically bright haze layer that reduces atmospheric transmission of some of the Sun's incoming radiation.
• The Anthropocene is the current geological era, characterized by the impact of human activity on the Earth's ecosystems.
• Geological Timeline

  
• 1880 saw the start of accurate records of global and ocean temperatures.
• The human enhanced greenhouse effect means that less hear escapes into space as more heat is re-radiated and there is more re-emitted heat.
• UK emissions peaked in 1971 - since then annual emissions have fallen by a third

  • Shift away from coal to natural gas
  • Nuclear power stations (1970's to 1980's)
  • Renewables since the 1990's
  • International obligations with regards to carbon emissions.
• In 2020, the UK's total GHG emissions were 49.7% below those of 1990 levels
• China emits 27% of global carbon dioxide and a third of the world's greenhouse gases.
• Without China successfully transitioning to a low carbon economy, achieving global climate goals will be impossible.
• China's CO2 emissions have tripled between 2000 and 2020 (not hampered by international protocols like Kyoto).
• China now consumes as much coal as the rest of the world together (50.5%) and is now the world's largest emitter of carbon in total.
• There is huge historical scientific evidence for global warming although there is still debate over it.
• Debates of climate change are shaped by a variety of agendas
• 97% of climate scientists support the view that global warming is taking place.
• There is debate on whether climate change is due to natural processes or anthropogenic causes
• Dissenters argued that rising temperatures in the first half of the 20th century were due to increased solar output and volcanic activity.
• In 1992 countries joined an international treaty, the United Nations Framework Convention on Climate Change (UNFCCC) which was established as framework for international cooperation to combat climate change by limiting average global temperature increases.