What does the illegal drugs trade have in common with the death toll from the Ebola epidemic? Or our collective failure so far to address climate change (the climate agreement in Paris marks the beginning, not the end, of the road) or the security council’s inability to stop the violence in Syria and Iraq? In each case – as with so many other crises in our world – they have at their heart a lack of political will and a failure of leadership. Narrow, short-term self-interests have overshadowed the understanding of how, in a truly global world, interdependent are our destinies.

Look at Ebola. We have known about the disease and the terrible risks it could pose for 40 years, yet we did not take effective action. Only when the death toll was mounting, borders were closing and there were fears of a global epidemic did we mobilise the resources needed.

Climate change, perhaps the world’s greatest challenge, is divisive only in political circles. The scientific community reached a consensus on the need to act years before the Paris agreement and the jury on whether leaders will mobilise the political will to actually implement it is still out. The illegal drugs tradecontinues to threaten public health and safety and undermine governance. Yet too many countries are still unwilling to recognise the failure of the war on drugs and adopt approaches that actually work.

In the economic and diplomatic sphere as well, we see this failure. Clamping down on tax evasion and using the money raised to invest in public services are two simple measures that would counteract the growing and damaging inequality in our world. This year will see the wealth of the top 1% exceed that of the remaining 99%.

The security council continues to reflect the geo-political realities of 1945 not the 21st century. But reform is selfishly blocked even though the security council’s loss of legitimacy may mean that we could eventually lose the only supra-national forum we have to resolve matters of peace and war.

The expertise, experience and evidence needed to solve these and many other pressing problems already exists. What holds us back is the lack of leadership that can galvanise the political will needed to deliver solutions. The world is experiencing a crisis of leadership, not a crisis of knowledge.

So how can ordinary citizens help bring about the change we need and encourage our leaders to actually lead? Let me give three clear answers.

First, if you live in a country with multi-party politics, make sure you vote. It may seem obvious or old-fashioned, but it is more relevant than ever. Research shows that young people in more and more countries are not exercising their democratic right to vote. Older voters outnumber young ones in every European country. We need to hear the voice of the young who, understandably, often take a longer-term view.

Second, make noise about the issues you care about. The digital age empowers individuals in unprecedented ways. You not only have access to more information than any previous generation, you also have the possibility of reaching out to many more people than was possible even decades ago.

Unless you campaign for effective solutions, you leave the space to those advocating extreme positions or allow political leaders to ignore problems. The fight against HIV and Aids during my tenure at the UN advanced substantially thanks to a committed, well-organised and extremely vocal body of civil society organisations who kept up the pressure on political decision-makers and on the pharmaceutical industry.

The same activism is needed today to press our leaders for effective, long-term approaches on drugs or climate change. We need moderate voices reclaiming the space of our town squares and especially the digital space which for now is an often unchecked playing field for those advocating unilateralism, ultra-nationalism and the politics of identity.

Lastly, use your power as a consumer, which is now unparalleled in history. Every time you buy a product or service, you are supporting a company. Before you decide which sneakers to buy or financial services to use, consider its business practices. There is a wealth of information out there on how businesses behave. Through our collective buying power, we can set the agenda and drive up standards.

When leaders fail to lead, I have seen time and time again how public opinion can make them follow. As we consider our resolutions for the new year, playing our part in using this collective power for good in 2016 should be high in our thoughts. As John Stuart Mill, the political philosopher, said almost 150 years ago: “Bad men need nothing more to compass their ends, than that good men should look on and do nothing.”

The Guardian