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

1. What do you think caused the increase in the temperatures in Singapore?

2. What is the climate change mentioned in the video?

3. What are the greenhouse gases?

4. What are the consequences of global warming?

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

Climate variability due to natural processes

a) changes in Earth’s orbit and angle of tilt

b) occurrences of sunspots and large-scale volcanic eruptions

Source: https://medium.com/@annamparsons33/if-you-think-earths-temperature-will-start-decreasing-then-you-should-look-this-cc6195b8dc84

Higher sunspot activity is linked to higher amounts of solar radiation emitted from the sun, leading to short-term increases in average temperatures. This is because areas surrounding the sunspots radiate more energy, which compensates for the lower temperatures of the sunspot areas.  The number of sunspots rises and falls with a cycle of approximately every 11 years. 

Particles spewed from large volcanoes eruption, like dust and ash, can cause temporary cooling by shading incoming solar radiation if the particles were launched high enough into the atmosphere. The cooling effect can last for months to years depending on the eruption. But volcanoes can also contribute to global warming when eruptions spew greenhouse gases into the atmosphere. Over millions of years this caused global warming during times in Earth’s history when extreme amounts of volcanism emitted large amounts of greenhouse gases. For instance, the 1991 eruption of Mount Pinatubo in the Philippines caused about a half-degree drop in global temperatures for two years. Check out the video below on how volcanic eruptions can cool the earth. 1991 Mt Pinatubo in Philippines and 1815 Mt Tambora in Indonesia (year without summer)

https://storymaps.arcgis.com/stories/3042b3b3d6104315957222d5cb402e6f

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.

1. NASA Milankovitch Cycles https://climate.nasa.gov/news/2948/milankovitch-orbital-cycles-and-their-role-in-earths-climate/

2. Climate in the past, present and future. Box 2.1 https://nca2018.globalchange.gov/chapter/2#box-2_1

3. Why climate change matters in Singapore? https://www.channelnewsasia.com/news/cnainsider/how-badly-climate-change-floods-drought-could-affect-singapore-12202206