Even if every country on the planet cuts emissions, the climate would still be screwed

Muir glacier 2 Alaska A planet devastated by climate change may seem like a distant future. But Earth is already experiencing the effects of rising global temperatures today.

Worldwide, the mean rate of sea level rise increased 50% in the last two decades. In 2017, temperatures have already reached their highest levels in history in some areas, from California to Vietnam. The past three years were the hottest on record.

These changes are caused by increasing levels of carbon dioxide and methane in the Earth's atmosphere, a product of human activity. And as New York Magazine's David Wallace-Wells recently noted, no single emissions reduction program we have today is enough to prevent climate disaster — not even the Paris agreement.

Even if every signatory country in the accord meets its current pledge for reducing emissions — including the US, though Trump has pledged to pull the country out of the agreement — the world is still projected to warm over 2 degrees Celsius by 2050. The Paris agreement points out this reality in a section titled, "Notes with concern."

Two degrees may not seem like much, but the rise would have substantial impacts. Scientists say that places that supply the world's food, including Southern Europe and much of the Middle East, Australia, Africa, South America, and China, would be in permanent, extreme drought by 2080. Flooding would become a serious issue near the coasts, where a third of the world's major cities are located, since sea levels are projected to rise by at least 10 feet by the end of the century.

Experts also warn that if the Arctic ice continues to melt, ancient diseases trapped in glaciers could get released. Plus, the world would face the extinction of many animal species and rising human mortality.

The planet has already warmed nearly 1 degree Celsius, and James Hansen, a renowned climate scientist at Columbia University, suggested in a recent paper that keeping global warming below 1.5 degrees is nearly impossible. Hansen suggested that hitting the goal would require negative emissions levels, which would mean capturing carbon and taking it out of the atmosphere.

To make matters worse, our best protection against the effects of rising carbon dioxide levels comes from so-called "carbon sinks" — patches of land and ocean that absorb large chunks of the carbon dioxide we pump into the atmosphere. But now those sinks may be at capacity, prompting the Earth to continue cooking even as emissions get curbed.

In a recent open letter, six prominent scientists and diplomats, including former UN climate chief Christiana Figueres and physicist Stefan Rahmstorf, wrote that the world has approximately three years before the worst effects of climate change take hold.

Published June 28, the letter urges governments, businesses, scientists, and citizens to address the world's greenhouse-gas emissions now. If emissions can be permanently lowered by 2020, they wrote, global temperatures will likely avoid reaching that irreversible threshold.

In the letter, the scientists propose six goals to hit by 2020:

Increase renewable energy to 30% of electricity use.
Draft plans for cities and states to ditch fossil fuel energy by 2050, with funding of $300 billion annually.
Ensure 15% of all new vehicles sold are electric.
Cut net emissions from deforestation.
Publish plan for halving emissions from deforestation well before 2050.
Encourage the financial sector to issue more "green bonds" toward climate-mitigation efforts.

But those aims are at odds with the priorities of the Trump administration, which has signaled that climate change mitigation is not on its agenda. Because of that conflict, the authors call for US cities and businesses to fight emissions and meet the Paris accord goals without the help of the federal government.

"We stand at the doorway of being able to bend the emissions curve downwards by 2020, as science demands, in protection of the UN sustainable development goals, and in particular the eradication of extreme poverty," Figueres said in a press release.

"This monumental challenge coincides with an unprecedented openness to self-challenge on the part of sub-national governments inside the US, governments at all levels outside the US, and of the private sector in general. The opportunity given to us over the next three years is unique in history."

Wallace-Wells emphasized in his recent New York Magazine piece that an enormous effort from the world's governments and citizens is crucial for staving off the worst effects of climate change. Whether the world will succeed in addressing emissions in a serious way, however, remains to be seen.

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