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Last year was officially the Earth's warmest sincerecord-keeping began in the 1880s, the WorldMeteorological Organization announced.
That means 2016 set a global heat record for thethird year in a row according to NOAA and NASA.
Not only was this the third consecutive year to rankhotter than all previous years, it also means 16 of the 17 hottest years on record haveoccurred since 2000, according to NOAA.
To put this in perspective, the last time we had a record cold year was 1911.
Temperatures over the Earth's continents and oceans in 2016 were 1.1 degree Celsius (1.98degrees Fahrenheit) above the pre-industrial average, according to the WMO.
That means we are already a majority of the way to the 1.5-degree warming goal set at theParis Climate Agreement in 2015.
Climate scientists say greenhouse gas pollution, which humans are creating primarily byburning fossil fuels and chopping down rainforests, likely contributed to the 2016 record.
And the pollution certainly is behind the long-term trend toward warming, scientists say.
"The spate of record-warm years that we have seen in the 21st century can only be explainedby human-caused climate change," said Michael Mann, director of the Earth Science Center atPennsylvania State University.
"The effect of human activity on our climate is no longer subtle. It's plain as day, as are theimpacts -- in the form of record floods, droughts, superstorms and wildfires -- that it is havingon us and our planet."
World Leaders to Sign Climate Agreement onEarth Day
Leaders from 130 nations are gathering at the UnitedNations to sign the historic climate deal reached inParis last December.
The signing happens on the 46th anniversary ofEarth Day. Since 1970, every year people around the world observe the day by doing differentactivities to clean up the environment.
On April 22, 1970, U.S. Senator Gaylord Nelson organized the first Earth Day with a "nationalteach-in on the environment."
Earth Day Network says 20 million Americans gathered in the streets, parks and meeting halls"to demonstrate for a healthy, sustainable environment" in large rallies across the country.
This year, more than a billion people will celebrate the day by working for a cleanenvironment.
U.N. Secretary-General Ban Ki-Moon has urged countries to take action to fix climate change.
"That is the only way which we can save this one, only, planet Earth."
Island nations are very vulnerable to the stronger storms and rising sea levels brought on byclimate change. One example is the Pacific island of Fiji. Super Cyclone Winston crashed into theisland nation last February, killing 44 people and causing $1 billion in damage.
Fiji's Prime Minister Josaia Bainimarama talked about their fear about the future:
"The frequency and intensity of extreme weather events such as Winston's is increasing. Andwe all have to be fearful about what this means — not only for ourselves, but for futuregenerations."
It was last December, in Paris, France that world leaders worked out the details for the historicagreement. It limits the rise in global temperatures to well below two degrees Celsius.
It provides a way to reduce greenhouse gas emissions — those include pollution fromfactories and the burning of fossil fuels like coal. The agreement calls for a way to stop theeffects of warming the planet. That includes moving towards using renewable energies, likewind and solar— or power from the sun.
Putting the plan into action will take several steps.
First, the 130 leaders gathering in New York Friday will sign the agreement. Then theirgovernments must ratify — or formally approve it — to put it into action.
Selwin Hart is director of the U.N. Climate Change Support Team.
He says the Paris Agreement must cross two important lines to become enforceable.
First, at least 55 parties to the United Nations Framework Convention on Climate Change mustratify the agreement. And those 55 countries must represent 55 percent of globalgreenhouse gas emissions.
China and the U.S. are the biggest contributors to the world's global greenhouse gases.Together, the countries are responsible for about 40 percent of the world's emissions.
Both the U.S. and China support the agreement. They are pushing for its early adoption by allthe nations.
The target date to start the agreement is 2020. That could change. If all the countries ratify itquickly, it could happen this year, or in early 2017.
I'm Anne Ball.
Scientists in Mexico say they may have found a way to cut production of methane, a gas linked to rising temperatures on the Earth's surface.
The scientists say their method may help reduce the methane released by cows, one of the main producers of the gas.
When talking about global warming, many people think of carbon dioxide, another heat-trapping gas. Studies have shown that large amounts of carbon dioxide in the atmosphere reflect heat back to earth, causing climate changes.
Methane is an even more powerful heat-trapping gas. Cows are known to produce high levels of methane when they eat and process food. Farm animals are responsible for 44 percent of all human-caused methane, according to the Reuters news service.
Researchers at the Autonomous University of the State of Mexico are studying how a cow's diet affects the production of methane. The researchers are using a specially designed machine to measure the effect.
Stefanny Hernandez is an assistant researcher at the university. She told VOA that, "approximately 95 percent of methane that is emitted by cattle is from breathing."
The scientists use the machine to try to capture the animal's breathing to examine the methane released, she explained.
Most of the gas is released when cows belch. The digestive bacteria in a cow's stomach causes the animal to expel the gas through its mouth.
There are an estimated 1.3 to 1.5 billion cows in the world. Each animal releases as much as 120 kilograms of methane per year.
The U.S. Environmental Protection Agency reports that, when measured in pounds, the effect of methane on climate change is more than 25 times greater than carbon dioxide over a 100-year period.
In addition, a 2006 United Nations report found that raising cattle produces more greenhouse gases than cars and trucks combined. This includes not just gases released by the cattle, but the effect of related activities, such as clearing forests to raise the animals.
Octavio Castelán is the head of the university's cattle and environment laboratory. He told VOA, "If we can reduce methane emissions, then we can rapidly reduce the effect on climate change."
As it is difficult to capture the gas released by cows for use as energy, one way to lessen its release is to change their diet.
Scientists in some countries are looking for ways to decrease cow methane. But, Castelán explained, while they are trying different plants and chemical compounds, those products would be too costly and difficult to bring to Mexico.
The Mexican researchers have found two animal food sources offering promising results: leaves from the leucaena tree and the flowers of the cosmos plant. Both plants grow in warm climates.
The researchers found that cows who ate grass mixed with the leucaena leaves belched about 36 percent less methane than a diet of grass alone. The cosmos flower reduced these emissions by 26 percent when mixed with the animal's feed.
In addition, the two plants do not have a harmful effect on milk and meat production. In fact, the researchers found that leuceana leaves improve the quality of cow milk. This can give Mexican farmers more reason to grow the plants and change their cattle's diet.
I'm Alice Bryant.