Prime Minister Justin Trudeau seemed to handle his recent visit with President Donald Trump extremely well.  Friendly, but not effusive, he focused on trade and avoided controversial issues. He skated around Trump's travel ban, refrained from mentioning Nordstrom and certainly avoided subjects like climate change.Remember climate change? Remember the simple fact that our planet is warming at an alarming rate due in large part to human activity? If left unchecked, scientists tells us it could soon lead to droughts, food shortages, rising sea levels, the disappearance of coastal areas and even entire islands, creating tens of millions of climate refugees and changing the very nature of our planet.Climate change seemed to be a trendy topic a few years ago, particularly around the time of Trudeau's election. Since then, despite some grumbling about the carbon tax, it seems to have fallen off the radar.  Oh sure, everyone laughed during the campaign when Trump proclaimed that climate change was hoax perpetuated by the Chinese, but he didn't spend much time on the subject so why should we? And anyway, didn't the Paris agreement signed a few years ago solve the problem?Actually the Paris agreement didn't solve anything. Although it is true that the nations of the world agreed to limit their carbon emissions on a voluntary basis in order to hold temperature increases to acceptable levels, the emission limits they each chose are not high enough to achieve the desired goal. As former president Barack Obama commented upon the US ratification of the agreement: “Even if we meet every target embodied in the agreement, we'll only get to part of where we need to go.” The agreement itself acknowledges the inadequacy of the planned targets and commits signatories to meet regularly over the coming years to assess progress and set bolder emission reduction goals. In other words, we are far from finding a solution.Whether we like to admit it or not, the world is facing a crisis of unparalleled proportions and we need American leadership. Although Trump campaigned on pulling the United States out of the Paris agreement, his stance softened slightly once elected. In a late November interview with the New York Times he admitted “some connectivity” between human activity and the warming of the planet, and said that he has “an open mind” when it comes to the Paris climate agreement.Little he has done since then has given reason for optimism. Appointing the former head of Exxon as secretary of state and a climate change denier as the new head of the Environmental Protection Agency (EPA) has not helped. Neither did encouraging efforts by Republican lawmakers to repeal Obama Administration regulations aimed at curbing the environmental excesses of the energy industry.Our planet is in danger. And hoping for the best while we wait for the chaos in Washington to settle can't be our strategy. Neither can musings by Prime Minister Trudeau last December that if the United States “takes a step back” from fighting climate change, “we should look at that as an extraordinary opportunity for Canada and for Canadians” to take a more prominent role in the green economy. The stakes are simply too high for adopting a “whistling past the graveyard” approach.Yes, this is bigger than just Canada. And we shouldn't second-guess Trudeau's longer-term strategy which seems to involve building a good personal relationship with Trump before engaging him on thorny issues such as climate change. Trudeau's mention of past Canada-US environmental agreements during his press conference with Trump and reference in their joint statement to “environmental co-operation” and “innovation, particularly in the clean energy sphere” were positive signs. Even Green Party Leader Elizabeth May admitted that: “There is definitely coded language that suggests that climate action is not off the table.”But this dance can only go on for so long. The urgency of the situation demands that the world's political leaders unite to press Trump on the issue of climate change. And the only effective way for them to do this is with the open and vocal support of the world's populations. We simply cannot afford to let the fight to curb climate change be a casualty of the Trump presidency — the stakes are too high.In his 2008 book Climate Wars, Canadian journalist Gwynne Dyer presents a futuristic glimpse of a world facing unchecked global warming. Using expert predictions, he outlines likely scenarios for different parts of the world.Although writing many years before Trump's candidacy for president, Dyer predicted that if serious action wasn't taken, the United States might need to build a wall in the not-too-distant future to keep out climate refugees from Mexico and Central America fleeing the droughts and upheaval caused by the warming planet.Let's ensure that climate change doesn't give Trump his wall after all.John Milloy is a former MPP and Ontario Liberal cabinet minister currently serving as the co-director of the Centre for Public Ethics and assistant professor of public ethics at Waterloo Lutheran Seminary, and the inaugural practitioner in residence in Wilfrid Laurier University's Political Science department. He is also a lecturer in the University of Waterloo's Master of Public Service Program.  John can be reached at [email protected] or follow him on Twitter @John_Milloy.