For the next two weeks, diplomats from more than 190 countries will gather near Paris to hammer out a new international agreement on climate change. This conference, known as COP21, is getting heavily hyped: We're already seeing chatter about whether this is our last chance to "save the world" or keep us below 2°C of global warming.

But that's ... the wrong way to think about what's going on in Paris. These climate talks, by themselves, won't fix global warming. They can't do that. They're not designed to do that. The actual goal is much more modest: to add structure and momentum to efforts that are already underway, in legislatures and laboratories and cities and boardrooms around the world, to reduce greenhouse gas emissions.

That may sound like hair-splitting, but it's a crucial distinction for understanding what these talks are all about. It's why many onlookers think a deal is vitally important, and others say it'll be a massive disappointment. Both things, in a way, are true.

The Paris talks will be very different from climate conferences of yore, when negotiators would try to craft binding global treaties that required nations to cut their emissions by set amounts, imposed from on high. See, for example, the 1997 Kyoto Protocol. That was a grand plan to save the world. And it failed, spectacularly. The US Senate refused to ratify Kyoto. Canada pulled out. And, crucially, fast-growing China and India never acceded to cuts. Emissions soared in the years after Kyoto:

The lesson learned was that no fancy UN accord could ever force countries to make wrenching changes to their energy systems that they didn't want to make.

So in recent years, the UN climate talks have shifted to a radically new model. Each country will start off by deciding for itself how it plans to tackle greenhouse gas emissions, taking into account its own unique domestic situation. This "bottom-up" structure has led to universal participation, which is no small thing. Since 2014, every single major emitter has submitted a climate pledge to the UN. Some highlights:

The United States is vowing to cut its greenhouse gas emissions at least 26 percent below 2005 levels by 2025, through policies like the Clean Power Plan to decarbonize power plants.

The European Union will cut emissions 40 percent below 1990 levels by 2030.

China has vowed that its emissions will peak around 2030 and that it will get about 20 percent of its electricity from carbon-free sources by then.

Brazil will cut emissions 37 percent below 2005 levels by 2025, with an emphasis on curbing illegal deforestation in the Amazon.

India will continue to reduce its carbon intensity, or CO2 output per unit of economic activity, in line with historic levels (though overall emissions will grow).

You can find a full list of these pledges, known in UN-speak as "Intended Nationally Determined Contributions" (INDCs), here.

Two realities: These pledges are plausible, and they are laughably inadequate

These individual pledges, which have already been designed and submitted, are the backbone of any new global agreement; they'll do virtually all the heavy lifting. They also have two notable features:

First, the pledges are plausible. They weren't dreamed up by remote UN bureaucrats. They were all freely submitted by national governments, based on what was deemed politically realistic and technologically feasible. The US pledge, for example, is rooted in the Obama administration's understanding of what's possible through existing executive authority. It doesn't assume Congress will miraculously pass new bills.

Second, these pledges are laughably inadequate to the task of preventing severe global warming. If you assume every country follows its pledge to the letter, global emissions will keep rising through 2030, and we'll be setting ourselves up for around 3°C of global warming by century's end. Happily, that's a major improvement over the end-times-ish 4°C rise we used to be on track for. Not so happily, it means we'll likely be zipping past the 2°C global warming mark, which has long been deemed unacceptably risky. Not good.

That's where these Paris talks come in. Over the next two weeks, negotiators will try to add support structures that, they hope, will allow these pledges to get stronger over time. They'll create transparency and verification mechanisms so that everyone can see whether countries are following through. They'll haggle over financing to help poorer nations. They'll discuss formal review process, allowing the pledges to be revisited and boosted in regular intervals.

There are no guarantees this will work. But, as political scientist David Victor explained, the idea is you start with what's plausible and try to iterate from there, through cooperation and political persuasion.

Or, if you like metaphors: Think of the countries making climate pledges as a bunch of out-of-shape slobs trying (and failing miserably) to qualify for a relay event. A Paris deal won't be able to force these people to train harder. But it can put their names up on a whiteboard, track their progress, work out gym subsidies for those who can't afford it, and facilitate peer pressure. Obviously the exercise is the crucial part, and that ultimately depends on each individual. But that other stuff can help.

So it's worth keeping these talks in perspective. A strong agreement out of Paris could help support ongoing efforts to reduce fossil fuel emissions and curb deforestation. But whether Earth warms 2°C or 2.5°C or 3°C won't be decided by these talks. That will depend on what future policies get enacted by individual countries, on how quickly we switch over to alternative energy sources, on how technology evolves. Tackling climate change is a vast, herculean task, the work of generations — and it will remain so no matter what happens in Paris.

Okay. So what should I watch for in the Paris climate talks?

There's going to be endless bickering in the next two weeks over a slew of issues. Some of it will matter; a lot of it simply won't. Ultimately, the key thing to watch is whether a final deal helps countries build on the climate pledges they've already made.

Before the Paris talks began, negotiators had already whittled down a draft agreement to about 50 pages, with a number of key issues left to be decided. Here are two important questions that are worth watching:

1) How often will pledges get reviewed and strengthened? Again, if you add up all of the world's current pledges, global emissions will keep rising through 2030 and the world will heat up by 3°C or so by century's end. That's bad. So, ideally, a final deal at Paris will set forth a structure whereby countries can periodically revisit and ratchet up those pledges.

The precise details matter quite a bit. US negotiators have pushed for a five-year review cycle; India has proposed a looser 10-year review cycle. There's also the question of whether countries would be pressured to strengthen their pledges during each subsequent review, to take into account, say, advances in renewable energy technology or faster-than-expected progress. See John Upton's piece at Climate Central for more on this debate.

Meanwhile, those pledges are worthless if they can't be verified in a transparent and consistent way. China's coal statistics are notoriously unreliable, for instance. Fixing stuff like that will be an important part of any final deal.

2) What sort of financing will be available to poor countries? In every climate conference, poor countries point out that they need help to decarbonize their economies and adapt to climate change. And since rich countries are responsible for the vast majority of carbon dioxide already in the atmosphere, it's only fair that they pony up. Most everyone agrees on this general principle. It's just hard to shake loose the funds.

Back in the 2009 Copenhagen climate talks, wealthy countries agreed to provide $100 billion annually in public and private money by 2020. A recent OECD report argues that they're now providing about $62 billion annually, but some critics accuse them of double-counting existing aid and loans. And poorer countries are now asking for even more in climate aid. India, for instance, has been told that it can't get rich the way the US, Europe, or China did — by burning lots and lots of coal. So, in turn, India has said it will need more than $160 billion per year in outside investment to make up the difference.

This is one place where the climate talks really could stumble. It's also one of the few places where congressional Republicans determined to sabotage a climate deal in Paris could actually matter. President Obama has promised that the US government will chip in $3 billion over four years to the UN's Green Climate Fund. But he has to ask Congress for that money, and the GOP seems unlikely to oblige.

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Climate talk aficionados will notice I left out reams of topics that will no doubt get plenty of press these next two weeks. But as Michael Levi nicely explains, most of this stuff is a bit of a sideshow.

For instance, the European Union and United States have been squabbling over whether the Paris agreement will be "legally binding" or not. The Obama administration's view is that the verification and review mechanisms should have legal force but the pledges themselves shouldn't. This way, the deal doesn't have to get ratified by the US Senate (which will never happen). You can read all about this dispute at Carbon Brief, but spoiler: Europe is not going to block a final deal over this issue. The US will win. Feel free to skip past this melodrama.

What counts as "success" or "failure" for these talks?

It really depends on what you're expecting.

If you're expecting a Paris climate deal that will lead to a world powered by 100 percent renewables or keep global warming below 2°C ... well, you're going to be disappointed. The current pledges don't add up to 2°C, as just about everyone and their climate-modeler aunt has now pointed out. And a Paris deal will be built around those current pledges.

Likewise, if you were hoping that countries would agree to a global carbon tax in Paris, as climate scientist James Hansen has been urging ... well, that's not going to happen either.

Instead, what the people involved in these talks are hoping for is something more subtle. A successful deal would mean that for the first time, countries are all working together on climate change, with every nation now crafting plans to address the issue. True, many of those plans are meager, but they're a starting point. Importantly, it would be a signal to investors and policymakers that climate action has momentum behind it, that decarbonization is the future. It would energize future talks. It would inspire additional commitments, such as Bill Gates's pledge to finance the world's largest clean energy R&D fund.

For many, a successful Paris deal will also have clear verification measures for existing climate pledges, as well as a frequent review process to allow those pledges to get stronger iteratively. This three-page brief from the Center for Climate and Energy Solutions offers a pretty realistic overview of what a "strong" deal would look like.

That leaves a question: Could future ratcheting and subsequent, increasingly ambitious global agreements keep us below 2°C? In theory, sure. But it would require a big ratchet. A new report from MIT and Climate Interactive looks at how national pledges would have to change between now and 2030 to stay below 2°C:

So, for instance, China would have to bolster its policies to ramp up low-carbon energy and phase out coal so that emissions peak by 2025 instead of 2030. The United States would have to cut deeply by 2030. It would take sweeping efforts to decarbonize homes, vehicles, power plants, and factories. Cleantech would have to proliferate far more rapidly. It's a heavy lift.

But that would be true with or without an agreement in Paris. If these talks collapse, if no deal emerges, the alternative is ... well, nothing really. The status quo. A period of drift and aimlessness on one of the most important questions facing the planet today. "This is it, my friends," Christiana Figueres, who chairs the UN Framework Convention of Climate Change, reportedly said last year. "I guarantee you, if we do not succeed in 2015 ... it will take 10 years to get everyone around the table again."

What else should I read on the Paris climate talks?