9 Mavromichali street
Phone: +30.697.428.6950
E-mail: info@greenjustice.org.gr

Browse: Green Justice » Environment » How do we know how warm or cold it was in the past?


Find article:

Subscribe to newsletter:

Did you know:

  • If just 25% of U.S. families used 10 fewer plastic bags a month, we would save over 2.5 billion bags a year.
  • Every year we throw away 24 million tons of leaves and grass. Leaves alone account for 75% of our solid waste in the fall.
  • Over 100 pesticide ingredients are suspected to cause birth defects, cancer, and gene mutations.
  • Every ton of recycled office paper saves 380 gallons of oil.
  • About 1% of U.S. landfill space is full of disposable diapers, which take 500 years to decompose.
  • Glass produced from recycled glass instead of raw materials reduces related air pollution by 20%, and water pollution by 50%.
  • Homeowners use up to 10 times more toxic chemicals per acre than farmers.
  • By turning down your central heating thermostat one degree, fuel consumption is cut by as much as 10%.
  • One ton of carbon dioxide that is released in the air can be prevented by replacing every 75 watt light bulbs with energy efficient bulbs.
  • The uncontrolled fishing that is allowed has reduced the amount of commercial species. Some species, up to one-tenth of their original population.
  • Already over half of the world's tropical forests have been lost.
  • The garbage in a landfill stays for a for about 30 years.
  • Every ton of paper that is recycled saves 17 trees.
  • Earth is 2/3 water. but all the fresh water streams only represent one hundredth of one percent.
  • 84% of all household waste can be recycled.
  • Computers pose an environmental threat because much of the material that makes them up is hazardous. A typical monitor contains 4-5 pounds of lead.
  • One gallon of motor oil can contaminate up to 2 million gallons of water.
  • Agriculture absorbs 74% of all water taken by humans from rivers, lakes, aquifers and wetlands against 18% for industry and 8% for municipalities.

In cooperation with:

How do we know how warm or cold it was in the past?

How do we know how warm or cold it was in the past?

Scientists today measure the Earth’s surface temperature using thermometers at weather stations and on ships and buoys all over the world. Such thermometer records cover a large fraction of the globe going back to the mid-19th century, allowing scientists to determine a global average temperature trend for the last 160 years.
Before that time not many thermometer records are available, so scientists use indirect temperature measurements, supported by anecdotal evidence recorded by diarists, and the few thermometer records that do exist. Scientists must rely solely on indirect methods to look back further than recorded human history.
Indirect ways of assessing past temperatures, using so-called temperature proxies, take measurements of responses to past temperature change that are preserved in natural archives such as ice, rocks and fossils.
For example, ice sheets form as snow builds up, with each year’s snowfall preserved as a single, visible layer. There are measurable chemical differences in snow formed at different temperatures, so ice cores provide a record of polar temperature going back around 250,000 years for Greenland and 800,000 years for Antarctica.
Yearly banding is also found in fossilised corals and lake sediment deposits, and each band has a specific chemistry that reflects the temperature when it formed. Growth rings in tree trunks can be wider or thinner depending on the climate at the time of growth, so fossilised trees can reveal the length of growing seasons. And fossilised or frozen pollen grains allow scientists to determine what plants were growing in the past, which can give us a good idea of the climate at the time.
Marine sediment cores provide temperature records spanning millions of years. They contain the fossilised shells of tiny marine creatures that preserve a chemical record of the sea temperature when they lived.
To make their temperature reconstructions as accurate as possible scientists have calibrated each proxy by testing how it changes in response to changing temperature. However, the further back in time we look, the more sparse the proxy temperature records become. Therefore the most reliable way to work out past temperatures is to combine different proxies – and to use data from many locations to screen out local temperature fluctuations.

• This article was written by Carbon Brief in conjunction with the Guardian and partners