Week 2 Reflections

What are climate change records?

Climate change records come from many sources. David Parker's Youtube video describes many of them. One that surprised me was data collected from oil wells: "Depth profiles of temperature in oil-drilling boreholes can be used to estimate the changes in air temperature over recent centuries".

Another interesting source of climate data is the Argo project, an array of around 3,000 profiling floats that provide observations from the global ocean. These float measure temperature, pressure and salinity from the surface down to 2000 metres. When the float resurfaces it transmits its data to satellites which also determine its position.

How do volcanoes affect climate change?

The air around us contains all manner of small particles and liquid droplets. These are known as aerosols. The bulk of aerosols are from natural sources, some of which is ash from volcanic eruptions.

Volcanic eruptions can affect the climate in three ways: the ozone effect; the greenhouse effect; and the haze effect. Satellite data has confirmed that major vocanic eruptions, such as Mount Pinatubo, can cause short term ozone depletion in the atmosphere. Volcanic eruptions can enhance global warming by adding carbon dioxide to the atmosphere. The haze effect that results in global cooling is mainly caused by sulphur rich gases from the eruptions combining with water vapour in the stratosphere to create sulphuric acid droplets which absorb solar radiation and scatter it back to space.

How is today’s warming different from the past?

The main difference is that current climatic warming is occurring much more quickly than in the past. The Earth is predicted to warm by between 2 and 6 degrees Celsius in the next century which is at least 20 times faster than found in the past.

What is the role of isotopes in determining temperatures from the past?

Oxygen exists in two stable isotopes and the ratio of these found in calcium carbonate from the shells of creatures found in rock formations can be used to estimate the temperature of the ocean when the shells were created. The same effect can be observed in oxygen found in ice cores. More details can be found here.

How have trees been used to reconstruct different climate variables across the world?

Dendrochronology is the science that uses tree rings dated to their exact year of formation to analyse processes in the physical world. For example, a broad tree ring would indicate a year of good growth and a narrow one a less favourable year. This can be applied to the study of the present climate and to reconstruct past climates. More details can be found here.

How can ice cores provide a record of atmospheric composition?

Air bubbles trapped in ice cores can provide a record of past atmospheric composition. More details can be found here.