Chances are you won’t make it in person to the March for Science in Washington DC, but you can be part of the ongoing Earth Day campaign to educate everyone about climate change, and its unprecedented threat to our planet.

The theme of this year’s Earth Day, on 22 April, is Environmental and Climate Literacy. The Earth Day Network, which coordinates the global awareness-raising day, is launching an ambitious drive to ensure every student in the world is “climate literate” when they leave high school - by Earth Day 2020.

You certainly don’t need to be a climatologist to talk knowledgeably about climate change, but it helps to have the key facts at your fingertips. So here’s a handy guide to get you up to speed on the climate change basics.

The Earth has been getting warmer - for 627 months in a row

2016 was the hottest year on record, according to separate analyses by scientists at NASA’s Goddard Institute for Space Studies (GISS) and the National Oceanic and Atmospheric Administration (NOAA). It was also the third year in a row to set a new record for global average surface temperatures.

This record-breaking heat is part of a long-term warming trend. The Earth’s average surface temperature has risen about 1.1 degrees Celsius since the late 19th century, when modern record-keeping began, and is projected to rise further over the next hundred years or so.

The warming, most of which has happened in the past 35 years, is being driven largely by increased carbon dioxide and other man-made emissions into the atmosphere.

We’ve now had 627 months warmer than normal, when compared with an 1881-1910 baseline. If you were born later than December 1964, you’ve never known a month cooler than average, according to Climate Central.

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Image: Climate Central

The Paris Agreement

Years in the making, the Paris Agreement, signed by 196 nations in 2015, aims to keep global temperature increase well below 2 degrees Celsius above pre-industrial levels, and if possible, below 1.5 degrees Celsius.

This can only be achieved if countries stick to their commitments to significantly reduce greenhouse gas emissions.

During his campaign, President Donald Trump promised to withdraw the US from the landmark agreement.

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Image: REUTERS/Ian Langsdon

Carbon dioxide emissions

Air bubbles in glaciers provide a record of temperature and carbon dioxide stretching back 800,000 years, so scientists know the planet has experienced global warming before.

But this "paleoclimate" evidence also shows that the current warming is happening much more rapidly than in the past.

The primary cause is the emission of greenhouse gases into the atmosphere, mostly carbon dioxide, which form a blanket that traps heat at the Earth’s surface.

Human activities such as burning oil, coal and natural gas and deforestation have increased the amount of carbon dioxide by more than a third since the Industrial Revolution began.

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Image: NASA

Freak weather

Rising global temperatures affect rainfall in many places and increase the chances of extreme weather events such as floods, droughts or heat waves occurring.

Climate-related disasters worldwide have more than tripled since 1980. The US experienced 32 weather events between 2011 and 2013 that each caused at least $1 billion in damage.

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Image: United States Environmental Protection Agency

Rising sea levels

The planet’s oceans are also seeing big changes – they’re becoming warmer and more acidic, glaciers and ice sheets are melting and sea levels are rising.

The Intergovernmental Panel on Climate Change (IPCC) projects a sea-level rise of 52-98cm by the end of this century if greenhouse gas emissions continue to grow, or of 28-61cm if they’re significantly reduced.

Polar ice

Arctic sea ice is not only shrinking, but the oldest ice is melting, which makes it even more vulnerable to melting in future.

But the real climate wildcard is Antarctica’s ice sheet. The IPCC estimated it could contribute about 20cm of sea-level rise this century, but also warned of the possibility it could be several tens of centimetres more if the ice sheet became rapidly destabilized.

Deforestation

Trees absorb carbon dioxide as they grow, acting as a "carbon sink". Cutting them down means more greenhouse gases entering the atmosphere, which speeds up the pace and severity of climate change.

Forests still cover about 30% of land, but some 50,000 square miles of forest are lost each year. That’s equivalent to 48 football fields every minute. In the Amazon, for example, around 17% of forest has been lost in the last 50 years.

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Image: REUTERS/Nacho Doce

Coral reef bleaching

In the past 30 years, the world has lost 50% of corals and it is estimated that only 10% will survive beyond 2050.

Climate change and rising ocean temperatures are the greatest threat, and are behind the mass bleaching along Australia’s Great Barrier Reef for the second year in a row.

Bleaching occurs when extreme heat, pollution or low tides cause coral to expel algae living in their tissues, turning them white. Coral can recover from bleaching events, but they are under more stress and if the algae loss continues they eventually die.

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Image: The Conversation

The impact on humans and animals

People are already suffering the consequences of climate change. Around 22.5 million people were displaced by climate or weather-related disasters between 2008 and 2015, according to the UN Refugee Agency (UNHCR). Climate change is also a factor in conflicts driving people from their homes.

The UNHCR says that natural resources such as drinking water are likely to become more scarce and food security will become an even bigger concern in future because some crops and livestock won’t survive in parts of the world if conditions become too hot and dry, or cold and wet.

Climate change is also threatening wildlife: using satellite data from NASA, scientists estimate a possible 30% drop in the global population of polar bears over the next 35 years. That’s because sea ice is their main habitat, and it is shrinking.

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Image: naturespicsonline.com