Climate

GEOLOGY | CLIMATE CHANGEs

WEATHER
OR CLIMATE?

Weather is the word we use to describe the atmospheric conditions in a particular place at a specific time. If you look out of your window, weather is what you can see going on right at this moment in terms of wind, rain, sunshine, cloud cover, temperature and other natural atmospheric phenomena.

Climate delineates the average pattern of weather of a place, over many years. If we have extremes in weather conditions, such as a long hot, dry summer or a very bitter winter, we are not necessarily witnessing the harbinger of a changing climate. Scientists requires decades of careful measurements and analysis before they can determine whether there has been a shift in climate. One of the longest, unbroken and richest scientific records of weather observations in the world are made at the Radcllffe Observatory in Oxford. Observations have been made at the observatory since 1767.

THE CLIMATE SYSTEM

We can see from this diagram (created by the BGS ©UKRI) that The Climate System has many components that interact with each other; a change in one component may have a positive or negative affect on others. An imposed change like this is known as a feedback loop. Feedback loops come in two varieties: negative and positive. A negative feedback loop reduces the effect of change and helps maintain balance. A positive feedback loop increases the effect of the change and produces instability. So, in terms of climate change, an example of a feedback loop is something that speeds up or slows down a warming trend in the atmosphere, in this case a positive feedback accelerates a temperature rise, whereas a negative feedback slows it down.

E.G. if the amount of solar energy absorbed on the Earth’s surface were to increase (perhaps due to large scale deforestation changing the albedo), then the global surface temperature (GST) would increase. This would lead to a decrease in the amount of global snow cover. As fresh snow has an albedo of 0.80 reflects more solar energy than bare soil which has an albedo of 0.17, vegetation (0.25) or water (0.06), so a decrease in the amount of land covered by snow would allow more solar radiation to be absorbed and so a positive feedback is initiated.

ALBEDO

Albedo, the fraction of light that is reflected by a body or surface. It is an important consideration in climatology since recent albedo decreases in the Arctic have increased heat absorption at the surface.

CARBON

Detail of arctic permafrost thawing in Alaska and Canada, global warming climate change co

The Carbon Cycle describes the global recycling of carbon atoms from the atmosphere into the Earth; and then released from the Earth back into the atmosphere.

CAUSES

The rock record shows that there have been a number of large variations in Earth’s climate in the past, each one caused by a set of unique circumstances.