climate change-g4 Flashcards
What is climate change?
Climate change is any significant change in the earth’s climate over a long period. The climate constantly changes, it always has and it always will.
What is the Quaternary period?
The Quaternary period is the most recent geological period, spanning from about 2.6 million years ago to today.
What have the climate patterns been like in the Quaternary period and even before that?
In the period before the Quaternary, the Earth’s climate was warmer and quite stable. During the Quaternary period, global temperatures shifted between cold glacial periods that last for around 100,000 years and warmer inter glacial periods that last for around 10,000 years.
The last glacial period ended around 15,000 years ago. Since then the climate has been warming. Since 1880 the average global temperature has risen by 0.85*C.
What is global warming?
Global warming is the term used to describe the sharp rise in global temperatures over the last century. It is a type of climate change.
What are the global effects of climate change?
- Most of the world’s glaciers and ice caps are shrinking
- Artic sea ice is less extensive than in the past, affected wildlife such as polar bears.
- Low lying islands such as the Maldives and Tuvalu are under threat from rising sea levels.
- Sea levels may rise my 1m by 2100, flooding lots of agricultural lands
How can scientists use Ice and Sediment cores as evidence for climate change?
- Ice sheets are made up of layers of ice- one layer is formed each year
- Scientists drill into ice sheets to get long cores of ice
- By analysing the gases trapped in the layers of ice, they can tell what the temperature was each year.
- One ice core from Antartica shows the temperature changes over the last 400,000 years.
- The remains of organisms found in cores taken from ocean sediments can also be analysed. These can extend the temperature record back at least 5 million years.
How can scientists use temperature records as evidence for climate change?
Since the 1850’s, global temperatures have been measured accurately using thermometers. This gives a reliable but short term record of temperature change.
Historical records, like harvest dates or newspaper weather reports can extend the record of climate change further back.
How can scientists use pollen analysis as evidence for climate change?
Pollen from plants gets preserved in sediment e.g at the bottom of lakes or in peat bogs. Scientists can identify and date preserved pollen to show which species were living at that time.
Scientists know the conditions that plants live in now, so preserved pollen from similar plants shows that climate conditions were similar.
How can scientists use tree rings as evidence for climate change?
As a tree grows it forms a new ring each year- the tree rings are thicker in warm, wet conditions.
Scientists take cores and count the rings to find the age of the tree. The thickness of each ring shows what the climate was like.
Tree rings are a reliable source of evidence of climate change for the past 10,000 years.
What are the natural causes of climate change?
- Changes in the earths’s orbit
- Variations in heat output from the Sun
- volcanic activity
What is the milankovitch cycle made up of?
Eccentricity, axial tilt and precession
Scientists believe that these cycles affect the timings and seasons of the Earth’s climate, In particular the 100,000 year eccentricity cycle coincides closely with the alternating cold(glacial) and warm(inter glacial) periods in the Quaternary period.
What is eccentricity?
This describes the path of the Earth as it orbits the Sun. The earth’s orbit is not fixed- it changes from being almost circular to being mildly elliptical. A complete cycle- from circular to elliptical and back to circular again- occurs about every 100,000 years.
What is the axial tilt?
-The earth spins on its axis, causing night and day. The earth’s axis is currently tilted at an angle of 23.5 degrees. However over a period of about 41,000 years, the tilt of the earth’s axis moves back and forth between two extremes-21.5 and 24.5 degrees.
What is precession?
This describes the natural wobble. A complete wobble cycle takes about 26,000 years. The earth’s wobble accounts for certain regions of the world- such as the northern Norway- experiencing very long days and very long nights at certain times of the year.
How does solar activity affect climate change?
The number of sunspots increases from a min to a max over a period of 11 years. the 11 year cycle is called the sunspot cycle.
When sunpot actvity is at a maximum, the Sun gives out more heat. Large explosions occur on the surface of the sun resulting in solar flares.
When sunspot activity is at a min, the solar output is reduced. This can lead to lower temps on Earth.
For example, very few sunspots were observed between 1645 and 1715, this coincided with coldest period ‘the little ice age’.
