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The climate of an area is how it behaves over a long period of time, usually over a period of 30 years or more. Areas of the world have differing climates due their position on Earth’ surface.
Frozen ships and shipwrecks shipwrecks on Lake Baikal in Siberia, Russia. The climate there is described as sub-Arctic with annual average temperatures of about –5°C.
Climate change
Climate change has occurred when there has been a significant change to normal weather patterns that have been sustained for a long time – between thousands and millions of years.
Earth has undergone natural cycles of warming and cooling.
Glacial period = long cold time. Last glacial period 115,000 to 11,700 years ago. Parts of Tasmania covered in ice, Kangaroo Island connected to mainland.
Interglacial period = long warm time. We are currently in one.
Concern about fast temperature rises. Evidence suggests human activities involved.
Kangaroo Island is located south-west of Adelaide, about 14.5 km off the coast. The star on the picture shows the location of mainland Australia. The island was connected to the mainland at the end of the last glacial period.
Human influences on climate change
It is clear that humans are influencing climate change. The concentration of carbon dioxide in the atmosphere has increased from 280 parts per million (ppm) before 1800 to well over 400 ppm in 2018.
Table summarises the influences that humans are having on the climate and how climate change is affecting global systems.
Effects of climate change
As carbon dioxide concentrations rise, Earth continues to warm. Over the past 100 years, Earth’s average temperature has risen between 0.4 and 0.8°C; 2016 was the hottest year and 2019 was the second hottest since records began. While people have varying opinions on the possible consequences of climate change, the effects of rising temperatures could have dramatic repercussions.
The Keeling curve shows the concentration of carbon dioxide in parts per million from 1959 to 2019 using measurements taken from an observatory in Hawaii. This positive gradient shows that carbon dioxide levels are continuing to increase.
Polar ice
Melting polar ice caps
Melting polar ice caps due to rising temperatures cause sea levels to rise. This puts low-lying areas like Osaka at risk of flooding. Melting ice also reduces the amount of sunlight reflected back into space, allowing more to be absorbed by the oceans, which in turn further increases their temperature and leads to even more ice melting and sea level rise.
Reflecting ice
Meltwater contributing to a greater volume of seawater is not the only risk caused by melting polar ice. Ice reflects the Sun’s radiation back into space, which has a cooling effect on the planet. Less ice means less radiation is reflected, which results in an increase in global temperatures.
Ocean density driving currents
Salt in seawater causes density differences that drive ocean currents, which distribute thermal energy, organic matter and nutrients. As seawater freezes less due to rising temperatures, ocean density decreases, potentially leading to stagnant water, affecting marine life survival.
How do human activities contribute to changing climates?
What are the impacts of changing climates on biodiversity and ecosystems?
How do changes in global temperatures affect the water cycle?
What are some examples of evidence for changing climates?
What are some potential consequences of rising sea levels due to melting polar ice caps?
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