Carbon in the sky and climate change: Earth Day by the numbers

Since Earth Day – the annual day for the environment – started being observed, global warming has dramatically worsened. Could carbon pricing be a silver bullet?

Thinking about climate change can be overwhelming, but some experts think humanity can still turn things around for Mother Earth [File: Andrew Kelly/Reuters]

Looking back over the past five decades, there’s been a fairly steady descent into our current climate crisis as ballooning populations and hungry economies have relied heavily on burning fossil fuels for power.

Thinking about climate change can be overwhelming. But for those of you who fear it’s too late to change the planet’s fortunes, take heart. Because some experts think humanity can still turn things around for Mother Earth.

Some find cause for optimism in expanding energy efficiency, electrification or geoengineering. Others believe that carbon pricing is the number-one solution to bake the true cost of emissions into the economies and reorient them towards a more planet-friendly trajectory.

Meanwhile, many are chuffed that United States President Joe Biden – the current occupant of the highest office in the world’s largest economy – thinks climate change is a real and pressing issue that demands aggressive action.

So on this Earth Day, here are some key numbers to get you thinking about the climate crisis – including a few that may even give you reason to think hopefully.


The year that the first Earth Day took place, with the goal of spreading environmental awareness and appreciation for nature. Organisers in the US started the annual event as a response to a large oil spill off the coast of Santa Barbara, California.


Parts per million (ppm), the concentration of carbon dioxide in the atmosphere 51 years ago when Earth Day began. The scientific consensus says that this number must be kept down to reverse the worst effects of global warming.


Monthly global average ppm according to the Bloomberg Carbon Clock now, in 2021 – a number that has increased substantially in the last half-century. The rapid rise in greenhouse gas emissions has caused a climate emergency, with harsh impacts such as heatwaves, flooding and droughts — all of which dislocate large numbers of people and cause grave economic consequences.

1.32 degrees Celsius

Amount of warming that has already occurred in the average global temperature above pre-industrial levels. Yet this mercury level can be mitigated by transitioning to renewable energy sources, halting methane pollution, promoting carbon removal technologies and stopping deforestation.

1.75 degrees Celsius

The approximate target of the 2015 Paris Agreement on climate change, which specifies that warming should be kept “well below” 2 degrees Celsius — an upper limit associated by some scientists with about 450 ppm of carbon dioxide in the atmosphere. Ambitious activists want 350ppm to be the goal.

50 billion

Metric tonnes of annual greenhouse gas emissions, which includes carbon dioxide as well as methane and other gases. This number, in theory, can be pushed downwards to net zero by phasing out emissions from power plants and motor vehicles, among many other activities.


Social cost of carbon per tonne used under former US President Donald Trump, whose administration chose not to factor in the wider effects of climate pollution — such as business losses from extreme weather and property damage during hurricanes. The number implies that Trump significantly underestimated the larger economic toll from emissions.


The new, interim cost set by the Biden administration for every tonne released into the atmosphere. However, that figure is temporary, as the Interagency Working Group on the Social Cost of Greenhouse Gases plans to put out a long-term number by next year that will influence how the US federal government approaches regulatory standards.


The minimum internal price of carbon, per metric tonne, that the United Nations Global Compact has asked companies to set. The world body encourages business leaders to help drive investment decisions that speed up the transition to a low-carbon economy.


The growing number of countries that already have enacted a direct form of carbon pricing, such as an emissions trading system or carbon tax. Twenty cities, states and provinces around the world also rely on carbon pricing mechanisms, with more slated to deploy them in the future.

13 percent

The fraction of annual global greenhouse emissions that are, according to the World Bank, currently covered by carbon pricing schemes. This includes cap-and-trade systems that put a limit on the amount of emissions rather than applying a tax or price for each tonne of carbon.

Source: Al Jazeera