Much has happened in the climate change arena over the past half-decade, culminating in the Paris Agreement, but much more remains to be done.
This issue of Nature Climate Change marks the fifth anniversary of the journal. To celebrate the event, we invited the inaugural chief editor, Olive Heffernan, to reflect on the way in which climate change research has evolved over the past five years (p335). In addition, we invited five eminent researchers to discuss previously published research — selected by the editors — that changed the approach of its respective field. Paul Stern (p341) discusses the lasting legacy of a landmark study examining drivers of climate change beliefs among US citizens (D. M. Kahan et al. Nature Clim. Change 2, 732–735; 2012). Ilan Noy (p343) looks at two papers (R. Mendelsohn et al. Nature Clim. Change 2, 205–209; 2012 and P. Peduzzi et al. Nature Clim. Change 2, 289–294; 2012) that advanced our understanding of the impacts of tropical cyclones by linking the physical evidence for their increased frequency with the increasing exposure of the world's population. Friederike Otto (p342) gives her take on a Perspective article (D. Coumou and S. Rahmstorf Nature Clim. Change 2, 491–496; 2012) that controversially linked certain types of extreme weather event, notably precipitation and heat waves, to climate change. Shang-Ping Xie (p345) revisits one of the first studies to examine mechanisms underlying the early-twenty-first-century 'slowdown' in global warming, including the role of oceans (G. A. Meehl et al. Nature Clim. Change 1, 360–364; 2011). Finally, Douglas Morton (p346) explains how a study using satellite data to map tropical forest carbon stocks (A. Baccini et al. Nature Clim. Change 2, 182–185; 2012) gave extra impetus to the so-called REDD+ policy aimed at reducing emissions from deforestation and forest degradation.
From its inception, we have strived to make the journal the principal venue for researchers and policymakers interested in both the causes of climate change, and its wider societal implications. We have also aimed to create a forum for debate among leading experts, providing a space to discuss successes, failures and roadmaps for future research and policy. With this in mind, we have selected 10 pieces from our archive that we feel reflect the quality and interest of the many contributions to the journal. These papers can be accessed for free for a limited time on our dedicated 5th Anniversary web page (http://www.nature.com/nclimate/focus/5th-anniversary/index.html).
Happily, most of the studies that we publish are well received by the community, often highly cited, and much discussed. For this, we owe much to the efforts of reviewers. Over the years we have tapped into the expertise of hundreds of researchers in a wide range of fields, all of whom have offered their invaluable services for free. Reviewers usually see at least two versions of a submitted paper, along with sometimes copious supplementary information, and responses from authors to earlier comments. This represents a significant commitment in time, but papers do benefit enormously from reviewer input, a fact often acknowledged by grateful authors. We therefore take the opportunity to express our profound gratitude to the many reviewers — both old hands and early career researchers — who help and advise us.
Olive Heffernan notes in her article that the journal launched in the shadow of the 15th Conference of the Parties (COP15) to the United Nations Framework Convention on Climate Change — known as the Copenhagen Summit — a meeting that was widely seen as a missed opportunity. Five years later, we live in the relative 'glow' of the climate agreement hammered out at the COP21 meeting held in Paris towards the end of 2015. Despite the low initial expectations of commentators, the Paris Agreement may well come to be seen as a landmark event, paving the way to meaningful action on climate change.
There is indeed reason for some degree of optimism that a low-carbon, climate-resilient world can be achieved, given the necessary political will. However, complacency at this juncture would be misplaced. Much depends on whether nations fulfil their pledges to significantly reduce greenhouse gas emissions, as specified in their 'Intended Nationally Determined Contributions', and the extent to which such commitments can be ramped up in future. But simply reducing emissions is not sufficient. There is wide consensus within the research community that limiting warming to 2 °C over pre-industrial levels by the end of the century — let alone achieving more ambitious targets such as 1.5 °C — will require that a regime of 'negative emissions' be in place by early mid-century. Right now, the omens do not look that good. Emerging technologies such as carbon sequestration and storage may in the end save the day. However, that requires huge capital investment, as would massively increased uptake of renewable energy sources, and concomitant modifications to power grids. At the same time, the world's growing population needs to be fed; people living in poor, developing countries need access to water, power and modern medical care; in short, social justice, equity and the need for economic growth and security must continue to be factored into the equation.
If there is one thing that the fifth anniversary of Nature Climate Change brings into sharp focus, it is that there is no time like the present to get serious about climate change. A lot has happened in five years, but a significant acceleration of efforts will be needed in the next five if the world is going to meet the challenges posed by climate change.