These are the impacts of climate change we will never be able to fix
In December, the United Nations Framework Convention on Climate Change met in Lima, Peru to begin drafting an international agreement to cut emissions and begin the process of halting climate change before it's too late.
But too late for what, exactly?
In its latest climate change report, the Intergovernmental Panel on Climate Change warned of certain "irreversible" impacts of climate change, which were likely to occur if carbon emissions weren't aggressively cut by the end of the century.
These are some of the effects that will stick around forever - or hundreds of years at the very least, making them irreversible for our generation, and possibly that of our children and grandchildren. And there won't be anything we can do about it.
Carbon in the atmosphere
It's hard to put an exact number on its lifespan because there are so many different ways it can be removed from the air - forests and the ocean are both "carbon sinks," meaning they're able to absorb carbon dioxide from the atmosphere.
Scientists have estimated that up to 80% of carbon dioxide that goes into the air is absorbed back out within a few centuries (still longer than any of us are going to be around). But the other 20% could stick around in the atmosphere for millennia.
Warmer temperatures
This long carbon life cycle is important because it means that the increase in global temperatures from these greenhouse gasses is also effectively permanent - the planet isn't going to be cooling back off any time soon.
The IPCC's latest report states: "Warming caused by CO2 emissions is effectively irreversible over multi-century timescales unless measures are taken to remove CO2 from the atmosphere," meaning unless we find a way to suck huge quantities of carbon out of the atmosphere - still a pipe dream at this point - the planet will be running hot for a very long time.
A hot planet has some dire effects that would also be "irreversible" until temperatures return to normal. These include:
Sea-level rise
The IPCC writes: "It is virtually certain that global mean sea-level rise will continue for many centuries beyond 2100, with the amount of rise dependent on future emissions." The Greenland and Antarctic ice sheets, which both contain massive amounts of ice, are two spots scientists are especially worried about because of their potential to cause large amounts of sea-level rise.
In fact, a study conducted by researchers from NASA and the University of California, Irvine, made headlines last year when it concluded that a quickly melting section of the West Antarctic Ice Sheet had entered an unstoppable and irreversible decline.
The melting area contains enough ice to raise sea level by about four feet. The melting is likely to be complete in the next several centuries by conservative estimates, NASA reported. And once that ice is gone, it's not refreezing - at least not while the planet stays at its current temperature.
Changing geography
Of course, one consequence of long-term sea-level rise is a permanently altered geographic landscape. We're already starting to see its effects, as coastlines are shrinking and islands around the world are slowly being washed away.
Even within this century, sea-level rise could swallow whole island nations, erode coastlines, and flood some of the world's most densely populated cities, forcing mass, inland-moving evacuations of people fleeing the rising waters.
Climate Central has produced a handy sea-level rise map of the US to illustrate the potential future impacts of the rising seas. Users can change settings on the interactive map to zoom in on specific locations and see what they'd look like under various levels of sea-level rise.
For instance, here's what lower Manhattan would look like after 10 feet of sea-level rise (the blue areas represent water):
But other parts of the world are looking at a much more urgent timeline. The President of the island nation of Kiribati, for example, recently bought 6,000 acres of land in Fiji to be used for evacuation purposes in the future. Land in Kiribati sits just six feet above sea level on average, and the ocean is expected to rise by 30 centimeters by about a foot by the end of the century.
Ocean acidification
This is bad news for certain types of marine organisms, including coral and some plankton, which survive by creating protective, calcium carbonate shells around their bodies. The more acidic the ocean gets, the harder it is for these animals to complete the chemical processes required to make their shells.
And this is another event that's sadly unstoppable by humans. As long as there's room in the ocean for more carbon, the seawater will keep on sucking it out of the air - meaning acidification could also continue for centuries, the IPCC warns.
Extinction
Some climate-related effects are unambiguously permanent. While warming, sea-level rise, and ocean acidification may taper off centuries down the road if we stop pumping greenhouse gasses into the air, extinction is forever.
In November 2014, the National Audubon Society published a report identifying 314 US bird species that are threatened by climate change, mostly from changes to their habitats. And that's just one class of animal in one country.
The World Wildlife Fund reports that the biggest current threats to wildlife are exploitation by humans (think overhunting and overfishing) and habitat degradation/loss. But scientists predict that climate change will soon be a major player in the extinction of wildlife as it changes habitats and alters ecosystems around the globe.
Many scientists already believe Earth is at the brink of a mass extinction, its sixth in the planet's history, but the first caused by the planet's human inhabitants. Recent research has suggested that 26% of all mammals, 13% of birds, and 41% of amphibians are already in danger, and many of these jeopardized species will be even more vulnerable as changing landscapes, shifting food and water availability, and rising temperatures threaten their ability to thrive.
Unfortunately, scientists are increasingly pessimistic that we'll actually be able to stay within the 2-degree limit. While the goal is not impossible, many experts have recently argued that the talks in Lima last November, which were fraught with disagreements and complicated negotiations, suggest that future carbon emissions reduction goals are unlikely to keep us on target.
While humans may not be able to stop some of the subsequent climate-related events or reverse them once they're happening, knowing what to expect means we can at least begin to prepare for the future.
Our preparations can include bolstering our coastal communities, putting more resources toward protecting wildlife, researching agriculture and food security under the expected future conditions, and - most importantly - cutting carbon emissions to prevent any worse consequences than we're already getting.