How do we know that our climate is changing?

Credit: Pixabay

In order to be sure that our climate has changed we need to know what it was like in the past

In recent years there’s been a greater emphasis placed on observing the climate, due to the detrimental effect that its change is having on our environment. But that’s only in recent years, and prior to this there will have been little, if any, observation being conducted on the climate. So how can we be sure that it is in fact changing?

Well it’s lucky for us that some forward-backward thinkers found a way to do it; actually they found quite a few ways.

Due to the interest in conserving our planet and the new technologies available, scientists observing the climate now have an inventory of equipment with which to accurately measure and observe our present climate. There are acronyms like SQUID (Superconducting Quantum Interface Device) and SST (sea-surface temperature) being banded around.  Specialised facilities, organisations and even satellites are all closely monitoring parameters on land, at sea and in the atmosphere. But when it comes to collecting climate data from the past (300 years previously) things aren’t quite so simple; a little initiative is necessary, shall we say.

The growth of tree rings are largely affected by temperature and rainfall. We can therefore use growth rate to broadly estimate changes to rainfall or temperature depending on the preferences of the tree. The only problem with this method is that growth is affected by a range of climatic factors so it can be difficult to distinguish between each. This method can also be used with coral as they too have seasonal growth rings that are affected by temperature (faster growth in warmer waters).

The examination of ice cores can be used to reveal air temperatures. By taking samples of ice scientists can examine air bubbles that have become trapped within the layers of snow. It is these air bubbles that show not only temperature but also precipitation, dust transportation and volcanic fall out.

Ocean sediments are made of fossil shells, which accumulate on the seabed as organisms die. A sample of these sediments can be collected using a steel tube, which allow fossils to remain in their chronological order of formation. Analysis reveals what species inhabited the different layers and from that it’s possible to estimate if the water was warm/ cold by the preference and abundance of the species.

Pollen records date back to the Devonian era and provide a unique and unusual insight into our past climate. Pollen is the powder that contains the microgametophytes or the ‘sperm’ of seed plants. Its can remain perfectly preserved during fossilisation as it is protection by its outer sheath, known as the sporopollenin. Even in a fossilised state the tiny pollen grains are identifiable thanks to their distinctive morphology. The abundance and distribution of pollen can be used to estimate temperatures, depending on the plants preferences.

Although there are data gaps and inaccuracies associated with these ‘indirect’ methods of climate measurement, they’re important in giving us something to compare current data with. In some cases this data can be combined with information collected from modern equipment, like Stevenson shelters, weather bouys and satellites.

In order to better estimate how our climate might change in the future, it’s important that we understand changes that have occurred in the past.

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