All countries need to take climate action. But there are some that, because of the size and structure of their economies, need to lead the way by phasing out harmful industries, investing in environmental conservation and restoration, and supporting a just transition away from fossil fuels on a global scale.

In fact, the world's top three polluters — the United States, China, and the European Union — account for 41.5% of annual greenhouse gas emissions, while the bottom 100 polluters account for just 3.6%, according to the World Resources Institute. 

Whether or not the goals of the Paris climate agreement can be achieved largely depends on how these and other UN members act.

As COP26 approaches, influential countries have the opportunity to generate global momentum for climate action and set the world on a path to keeping temperatures from rising more than 1.5 degrees Celsius above pre-industrial levels. 

It’s an opportunity that will require enormous effort and investment, but one that also promises enormous benefits. In fact, investing $1.8 trillion in climate adaptation efforts would prevent $7.1 trillion in climate impact costs. Investing in climate mitigation, meanwhile, will create jobs, protect people’s health, and allow the global environment to recover.

There are some heavy-polluting countries such as Russia and Brazil that are actively undermining global climate action by weakening their commitments under the Paris climate agreement.

But there are dozens of other countries with similar climate footprints that have shown a willingness to take climate negotiations seriously and could still make significant commitments at the upcoming conference.

These five countries in particular need to go big at COP26. 

1. Australia

Australia has lagged on climate action, earning a rating of “highly insufficient” from the Climate Action Tracker (CAT). The country is still heavily dependent on coal and earned the worst score in a report by the United Nations analyzing how countries have responded to climate change.    

While Australia announced Tuesday it would pursue “net zero” emissions by 2050, it has presented few concrete details on how it aims to achieve this goal. Further, the country hasn’t set stronger emissions reductions targets for 2030, the date by which global emissions have to fall by half, according to the United Nations.

Australia can build on the goodwill it generated by committing to net zero by setting an ambitious emission reduction target for 2030 and a plan for how it is going to be achieved, and by increasing its international climate financing toward the country’s fair share of the $100 billion per year developed countries promised in 2009.

2. China

China accounts for 27% of the annual greenhouse gas emissions that are heating up the planet. The country’s rapacious economic growth and dependency on coal and natural gas make it arguably the most critical player in climate change discussions.

China has made tremendous strides in recent years. The country has vowed to stop funding coal production abroad, agreed to reach carbon neutrality by 2060, and boasts the largest renewable energy portfolio in the world. 

China has outlined plans to reduce emissions per unit of its gross domestic product by 65% compared to 2005 levels, get 80% of its energy production through renewable means by 2060, and also significantly expand forest coverage in an attempt to achieve harmony between the natural world and human civilization. 

While these targets are a good start, the country could go even further given the urgency of the situation. Without dramatic emissions reductions, the global carbon budget for keeping temperature increases below 1.5 degrees Celsius will be burned through within a few years. China has the opportunity to commit to stronger emissions reductions targets at COP26 as a way to become the global leader on climate action.  

3. United States 

As the largest historical emitter of greenhouse gas emissions and the primary architect of the global economy, the US has unrivaled responsibility when it comes to addressing the climate crisis. 

But for the past decade, the country has failed to live up to a promise it made toward international climate finance. Wealthy countries agreed to fund $100 billion in annual climate mitigation and adaptation in developing countries but have not yet mobilized this amount. The US, in particular, provides far less than its fair share considering the size of its economy. At COP26, US representatives can finally make amends by pledging $40 billion per year to this cause. 

There are other ways the country can show its commitment to climate action. President Joe Biden vowed to halve the country’s emissions by 2030 compared to 2005 levels, but the plausibility of this plan hinges on whether the country can pass meaningful climate legislation. The latest effort to accelerate the transition beyond fossil has stalled in Congress and could be gutted of key provisions. The Biden administration will have to fight to maintain these provisions to put the country on the path to halving its emissions. 

4. India

As a top emitter of greenhouse gases, India has to significantly restructure its economy to align with the Paris climate agreement. But it would be unfair to expect an emerging and developing country like India to fully fund this transition. Instead, wealthier countries need to step up and fund adequate levels of climate mitigation and adaptation around the world, including in India. 

India has already made major progress toward its 2030 emissions reductions and renewable energy generation goals, which means it has an opportunity to set even stronger targets at COP26, including vowing to phase out coal production. The country can also use its growing clout to create more assistance for developing countries, according to the Diplomat.  

5. Canada

Canada has presented itself as a leader on climate action on the global stage, but its efforts have been deemed highly insufficient by the Climate Action Tracker, which notes that the country’s policies are in line with 4 degrees of warming. 

The country must first help to reach the $100 billion climate finance target to ensure that developing countries can transition their economies. Secondly, Canada has to develop a stronger emissions reductions plan and back it up with concrete policies such as increased carbon pricing, an accelerated timeline for all-electric vehicles, new targets for reducing methane, and investments in environmental restoration.