Climate Changes As Always
How is the weather today? Blue sky, no rain, warm temperature: a perfect day to go hiking. It’s better than yesterday. It was so rainy and cold, I thought we were back in winter! Isn’t impressive how the weather is changing from a day to another one?
Unlike the weather, climate is more predictable and stable. On a certain region of the Earth, as a certain period of time, it is possible to have a good guess on the temperature and precipitation regime.
Book your skiing holiday on winter it’s better (if you are from the northern hemisphere!).
To define a climate, weather parameters such as temperature and rainfall have to be measured during a period of 30 years — a human generation. This climatic unit is called a “clino” and is used to compare climate in time or space by climatologist.
At the human generation scale, climate is pretty constant. However today I want to tell you that climate have changed for a very long time.
To start what influences the climate?
Climate is influenced by many factors. The primary factor is the Earth position in relation to the sun and the quantity of solar radiation our blue lovely island receives from this ball of fire.
Think of the day and night, probably the most obvious, nights are cold and day are warm. You don’t tan during the night because the sun doesn’t send any energy on your side of the Earth. While you are sleeping or getting drunk with friends, the other side of the planet has a sunny day. All of this exist because the Earth turns on itself.
Seasons are also a consequence of the strange position of the Earth around the sun. The Earth doesn’t have a straight obliquity, but an inclination of 23°, this explains the seasons! This inclination also vary between 22° and 24° on a 41 000 year-cycle. This may look like a useless information at our human scale, but for the climate it’s crucial since the obliquity of the Earth will change its exposure to sun radiation and so the quantity of capted radiation.
Another complex thing about the Earth relationship with the sun is its change of elliptic revolution. Sometimes the Earth turns around the sun in a perfect circle and sometimes it turns on an ellipse (egg like shape). When I say sometimes, I mean every 100 000 years. Which again is pretty unimportant for us, human, but quite a big influence on Earth climate changes. All these factors are the first one to change the climate.
It exists other factors which may influence the climate more or less globally. Most of them depend on the land cover. The quantity of solar radiation captured by the ground depends on the soil and plants covering it. For example snow and ice reflect all the sun energy back to space and don’t capture any heat. Plants catch the sunlight to photosynthesize and grow. Moreover they transpire a lot to cool down their body and bring the sap up there. Be aware that a oak tree can transpire 100 gallons of water a day! To a certain extent, transpiration cools down the atmosphere and influences air flows.
In the last hundred thousand years, climate has change a lot. It has also changed a lot before, but I’m too lazy to tell you all the story.
In the last hundred thousand years we had different ice ages: Gunz 670 kBP, Mindel 470 kBP, Riss 130 kBP, and the last one Würm 20 kBP. In the last ice age, the ice cap was covering the Earth up to the north of france and the north of the USA. A chilly time, I would say. Between the Riss and Würm ice age, there was an interglacial period when the climate was warmer and the sea level was 5 m higher because of the ice cap melting. According to ice sample and oxygen isotope studies, the climate was estimated to be 5°C warmer than today.
There is something scary about the change in climate. Today we are 7 millions and we highly depend on climate to survive. Many people today highly rely on the weather to survive. Aridity or frost can highly reduce yield and thus livelihood. Climate has always changed, plants and animals have always survived. I would even say they survived better to the past climate change than to humankind.
We, human, are probably influencing the climate. Climate is probably changing faster thanks to us. But is it really a problem? The 1.7 millions species of animals and plants will probably recover as they always did. Climate change may be a problem only for 7 billions Earthlings lost on a rocky island in a wide and unfriendly space.
