We are now at a tipping point that threatens to flip the world into a full blown climate emergency. As the poorest and most vulnerable people of the world endure the increasingly damaging impacts of a warming world, tired excuses and calls to delay action are no longer acceptable.

Economics aside, this is a moral and ethical challenge of the highest order. If ministers leave the UN climate talks in Warsaw this week without a clearly defined roadmap to accelerate the transition to a low-carbon world economy, our window of opportunity will become smaller yet again.

Just six months ago, the world entered a new danger zone when concentrations of carbon dioxide in the atmosphere passed 400 parts per million for the first time in recorded history. It came in a year of furious weather events. We saw a single tornado wipe out an entire town in Oklahoma, soaring temperatures and unseasonal wildfires burn in Australia months before summer, and a new breed of super typhoon smash into Palau and the Philippines leaving thousands of precious souls in its wake.

The Intergovernmental Panel on Climate Change has confirmed that the debate over climate science is over. As US Secretary of State John Kerry said to Pacific leaders during their recent meeting in the Marshall Islands, “the science is clear, irrefutable and alarming.”

But our response to this gathering crisis is falling well short. We are barreling towards 4C or more of warming before the end of this century. This is a death sentence for many of the world’s low-lying countries, and would fundamentally change life on Earth as we know it.

The opportunity to change course and keep warming to below 2C is there if we have the will to take it. While Japan’s reneging last week on its Copenhagen targets was damaging, and the signals from Australia deeply troubling, those of us that are actually serious about tackling climate change must forge ahead with purpose. We must show the world that climate action is not voluntary, but essential and firmly in our collective interest. Our coalition of ambition must grow.

Ministers in Warsaw should have two broad tasks in mind: finding ways to more urgently reduce emissions, and building political momentum to ink a new global agreement in 2015. But this agreement will not come into effect until 2020, and the temptation to delay action is seemingly too much for some to resist.

Succumbing to that temptation would lead to more than just a poison apple. It is a pathway to disaster. Instead, we need to be talking a different language: the language of opportunity, leadership and the benefits that come with the transition to a more sustainable and secure world abound with clean energy.

Negotiations in Warsaw come at a critical time. They represent a crucial step on the road to UN Secretary General Ban Ki-moon’s climate summit next September, and the annual climate talks in Peru at the end of2014 that will be the culmination of what many have already labeled the “year of ambition.” The loose emissions targets and trajectories agreed in Copenhagen in 2009 are nowhere near enough.

As the Ki-moon has made clear before, his summit cannot merely be a stepping stone to a new agreement in 2015, but must deliver “concrete action” to ensure that global emissions peak before 2020, and get us back on a pathway to a safe climate future.

Even as we witness the disasters and despair of a warming climate, it’s important to remember that for every climate laggard, there is also a leader. Vision, leadership and concrete action is what’s required to shift the political paradigm on climate change.

Just two months ago, the leaders of the Pacific Islands Forum met in the Marshall Islands, where they adopted the Majuro Declaration for Climate Leadership and pulled together a list of ambitious plans to transition their island economies to renewable energy. While this will put little more than a dent in global emissions, the Pacific message to the visiting big emitters, including the US and China, was simple: if we can do it, so can you.

It is this spirit that has seen countries like Germany achieve a 59% renewable energy peak last month, President Obama start to turn the tide on previous US inaction by launching a new Climate Action Plan that includes action to begin the phase down of coal power, and China’s statement last week that it intends to usher in stronger emissions reductions in its next Five Year Plan, due in 2015.

All these initiatives send a strong message that clean energy and a safe climate go hand-in-hand. This is why island states at the negotiations in Poland are proposing a ‘Warsaw Workplan’ to quickly reduce emissions by accelerating the uptake of renewable energy and improve the efficiency of energy use and supply.

Warsaw must be the next step to building a new wave of climate leadership. If ministers in Warsaw point us in the right direction, we believe that cities, business, civil society and local communities are ready to act, and will follow suit. Waiting until 2020 before we increase our ambition would be irresponsible, and send a signal that despite unequivocal scientific evidence that we are dangerously warming the world, our leaders are willing to gamble with our future and that of the planet.

The clock is ticking, the temperature is rising, the oceans are swelling, and the body count is growing. As much as we need signals of action for tomorrow, action today is what will count most.

• Tony de Brum is the minister-in-assistance to the president of the Republic of the Marshall Islands, which currently chairs the Pacific Islands Forum; Mary Robinson is the former president of Ireland and founder of the Mary Robinson Foundation for Climate Justice; and Kelly Rigg is the executive director of the Global Call for Climate Action which is a network of more than 400 NGOs.