Space & Innovation

Earth Hour: What Is the Carbon Footprint of an Email?

Find out how seemingly harmless everyday actions also contribute to emissions of carbon dioxide other greenhouse gases.

Sending a text message or email, eating an apple or watching TV -- each of these activities has a different carbon footprint.

People around the world are getting ready to mark Earth Hour by turning out the lights on Saturday from 8:30-9:30 p.m., but a long list of seemingly harmless everyday actions also contribute to emissions of carbon dioxide (CO2) and other planet-harming greenhouse gases.

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Total global emissions in 2010 were estimated at 49 gigatons (Gt or billion tons) of CO2 equivalent (CO2e).

Email and Internet Even a short email is estimated to have a footprint of 4 grams (0.14 ounces) of CO2e (gCO2e) -- including greenhouse gases produced from running a computer, servers and routers and the carbon produced in their manufacture.

An email with a large attachment emits about 50 gCO2e, and a spam message, not even opened by the recipient, is responsible for 0.3 gCO2e.

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The annual global footprint of spam is equivalent to 3.1 million passenger cars on the road in a year, using 2 billion gallons of gasoline.

A web search on an energy-efficient laptop leaves a footprint of 0.2 gCO2e, and on an old desktop computer about 4.5 gCO2e.

A cellphone text message comes at a cost of about 0.014 gCO2e.

Shopping A plastic grocery bag leaves a footprint of 10 gCO2e, and a paper bag 40 gCO2e.

Drinking A pint of water from the tap generates 0.14 gCO2e compared to 160 gCO2e for a 500 ml store-bought bottle.

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A large cappuccino comes at 235 gCO2e, compared to 21 gCO2e for a cup of black coffee or tea for which just enough water was boiled.

Leisure An hour of TV watching on a 15-inch LCD screen yields 34 gCO2e, compared to 88 gCO2e on a 32-inch LCD screen, and 220 gCO2e on a 24-inch plasma screen.

A mile of cycling powered by a meal of bananas would be responsible for 65 gCO2e, compared to 260 gCO2e for a mile powered by cheeseburgers.

Sources: "How Bad Are Bananas" by Mike Berners-Lee, Fifth Assessment Report of the UN's Intergovernmental Panel on Climate Change, McAfee study "Carbon Footprint of Spam".

As spring kicks in, our planet pics take a decidedly green hue, from the Northern Lights, to a verdant Alaskan park and a river that turns color in a flash. Above, canola flower fields cover the mountainous landscape of Luoping County, China.


Daily Overview

, satellite imagery courtesy of Digital Globe

When the sea ice that blankets the Arctic Ocean hit its yearly peak on Feb. 25, the maximum area was a record low. Animals like polar bears and walruses depend on it to reach their food, and diminished ice makes the search for sustenance more difficult. Above, a polar bear travels across sea ice in Alaska's Beaufort Sea.

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A Palestinian woman picks wild mustard flowers which grow in the untilled fields across the Gaza Strip.

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A solar eruption on March 17 was strong enough make the Aurora Borealis much more dramatic than usual. Here’s a shot of the Northern Lights, as seen from Narva-Joesuu, a town of just 2,600 residents on the Baltic seacoast of northeastern Estonia. Between September and March, the country is a traditional tourist destination for those who hope to see the Northern Lights.

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The Chicago River has been dyed green every St. Patrick's Day for the last 50 years. After the river is colored by a powdered vegetable dye, it can take several days for the green to dissipate. Workers from the Plumbers Union Local 130 who add the dye on St. Patrick's Day

say the biodegradable dye is safe

and was originally used to find illegal dumping in the river.

How the Chicago River Turns Green on St. Patrick's


National Park Service

tweeted this shot of a moose in Denali: "Doesn't get much better than the #firstdayofSpring and #HappyDay!"

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Durrat Al Bahrain will consist of 15 connected, artificial islands (including six atolls, five fish-shaped and two crescent-shaped). Construction costs are estimated at $6 billion and the project is slated for completion in mid-2015.


Daily Overview

, satellite imagery courtesy of Digital Globe

Salamanca -- one of 21 districts in Madrid, Spain -- is one of the city’s wealthiest areas and contains some of the most expensive real estate in the country.


Daily Overview

, satellite imagery courtesy of Digital Globe

The U.S. Army Corps of Engineers use levees, floodways and dams to control the Mississippi River. Their mission is to prevent the river from abandoning its current course, to protect port cities like New Orleans and Baton Rouge.

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