Natural variability of climate

What is the natural variability of climate?

1. Evidence of past climates

a) episodes of cooling and warming over geological time

b) evidenced by data on seafloor sediment and oxygen isotope

2. Changing climate zones

a) indicated by temperature as the most important parameter

b) evidenced by expansion and contraction of main climatic zones



Climate has changed in the past through natural causes, on timescales ranging from millions to hundreds of years. Average temperatures have increased markedly in the past 50 years.

Watch this animation on http://climate.nasa.gov/keyIndicators/#globalTemp - move the slider to see the increase in global surface temperature over time.

What is the general trend of temperature changes since 1880?

• Are there periods of temperature decrease and when?

• Are there periods of temperature increase and when?

• What has been the trend in temperature changes since the 1970s? 

http://olevelgeog.blogspot.com/2018/01/climate-change-singapore.html

Scientists determine the past climates of the Earth by analysing sediments from the seafloor and oxygen. Scientists study oxygen isotope levels by extracting sediments from the seafloor. The graph above shows the earth’s average temperatures in the last 1,000,000 years. Temperature fluctuates between warm and cold in fairly regular cycles.  

The sediment cores record past climates through the varying oxygen isotope levels in the layers of sediment. When the Earth’s climate is cool, there is a higher concentration of heavy oxygen (i.e. oxygen-18 isotope) in the ocean.

During an ice age there is more Oxygen-18 in ocean water. This occurs because Oxygen-16 is lighter and is more easily evaporated from the oceans. During ice ages, Oxygen-16 is transferred from the atmosphere to the land as snow and becomes trapped in the ice caps.

When the Earth experienced cooler temperatures (also known as glacial period) 18,000 years ago, large ice sheets were formed over continents. These continental ice sheets melted away when the Earth began experiencing warmer temperatures (also known as interglacial period). 

https://www.cdm.org/mammothdiscovery/wheniceages.html

Click on this link to watch the video on warmer and wetter Singapore:  http://olevelgeog.blogspot.sg/2013/10/warmer-and-wetter-singapore.html

Scientists projected average surface temperatures across the world will increase by at least 0.3°C – 1.7°C and at most between 2.6°C and 4.8°C, by the years 2081 to 2100, sad the Inter-governmental Panel on Climate Change report. Applied to the Southeast Asian region, this could translate to between 0.5 to 1°C, or 3 to 4°C, according to estimates from Singapore's Centre for Climate Research (CCRS). Taking the most severe scenario of 3°C, Singapore will see daily maximum temperatures of 34°C more often, and rainfall will increase by 25 per cent every 20 years.

As it is, Singapore's temperatures have increased by more than double the rate of the rest of the world — 0.26°C over the past 60 years as compared to 0.12°C. Rainfall intensity has also increased to 107mm from 80mm per hour over the past 30 years, but not necessarily due to global warming, said the CCRS in a statement released by the National Environment Agency. Another key measurement scientists are watching is sea levels, which they project will also increase, depending on the level of greenhouse gas emissions the world produces. The report also cites the melting of the Greenland Ice Sheet, which it predicts will take over a millennium at least to liquidate completely, but when it does, average global sea levels will rise by up to 7m.

Source: http://sg.news.yahoo.com/singapore-to-get-warmer--wetter-over-next-century--report-030148990.html


Here are some common misconceptions about climate change from the National Climate Change Committee from the link above.

Global warming vs climate change

These two terms are often used interchangeably, but they have different meanings.

Global warming refers to the increase in the Earth’s average temperature. Climate change, on the other hand, does not only refer to global changes in temperatures, it also refers to changes in weather patterns due to rising temperatures over a long period of time. Climate change brings about more occurrences of heat waves, droughts and heavy rainfall in various parts of the world.

Ozone depletion

The depletion of the ozone layer and global warming is not the same thing, and neither is one the cause of the other. The ozone hole is caused by human-produced chlorofluorocarbons (CFCs), while global warming is caused by excess greenhouse gases produced by human activities released in the atmosphere.

https://earthobservatory.nasa.gov/blogs/climateqa/are-the-ozone-hole-and-global-warming-related/

As shown on the NASA blog above, the ozone hole in fact has a cooling effect cos ozone can help trap heat.

The only similarity is that both can be linked to CFCs.

CFCs can cause ozone depletion aka the ozone hole and also is a greenhouse gas that traps heat.

Ozone hole does not cause global warming. 😨

https://www.ucsusa.org/global-warming/science-and-impacts/science/ozone-hole-and-gw-faq.html#.Wvq5pGnmg0M

Carbon monoxide

Carbon monoxide is an air pollutant, and can cause harm to our health. Although it contains one part carbon, similar to carbon dioxide (a greenhouse gas that contributes to climate change), carbon monoxide is not a direct contributor to climate change.