<p>Five years ago, the United Nations Paris climate agreement set a ceiling for global warming at well below 2 °C, ideally 1.5 °C relative to pre-industrial levels.</p>
<p>To achieve this everyone from the United States, China, the European Union, to the technology firm Microsoft and even an alliance of European airports are saying they will achieve “net-zero” greenhouse gas emissions this century.</p>
<p>But what is Net Zero? And is it the solution to global warming?</p>