Last month was the hottest April globally, according to new figures released by NASA on May 15. According to statistics, the temperature of the land and sea was 34 degrees warmer in April than the average temperature for the month between 1951 and 1980. April has become the seventh month in a row to break global records, making 2016 more likely to beat 2015 as the hottest year in history. Piers Forster, professor of physical climate change at University of Leeds, UK, and Chris Rapley, professor of climate science at University College London, explain why the temperature is heating up.

Piers Forster, professor of physical climate change at University of Leeds and member of the Royal Meteorological Society: “We need to urgently reduce emissions but this is not enough”

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Why are we witnessing such a global trend?

Piers Forster

Piers Forster

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Long-term global temperatures are rising due to greenhouse gas emissions. We expect month to month variation on the background warming trend. This is due to changing ocean circulation and random events such as volcanoes. Recently heat has been coming out of the ocean and adding to the longterm warming. Between 1998 to 2014 the ocean was absorbing heat which slowed the warming. Now it is giving that heat back out and we are in a period of surging temperatures.

Is it surprising for scientists?

Since 2005 it was predicted that temperatures would start increasing rapidly again, but it was hard for us to give a specific date as to when temperatures would start surging. We knew last year that 2016 was very likely going to be warmer than 2015.

What impact could it have?

We are already seeing the impact around the world: Increased flooding, droughts and sea-level rise; more heavy rainfall events. Corals are dying from warmer seas. We will also see impacts on food production. Some crops such as wheat gets killed by hot temperatures (when it’s greater than 30 degrees Celsius at their time of flowering).

How should we deal with this problem?

We need to urgently reduce emissions but this is not enough as temperatures will still rise for several decades. We therefore need to build better towns and cities, build flood defenses and develop new crop varieties to cope with the heat. 

Technological and natural ways of cooling the planet are also needed. We need to capture the carbon dioxide in the atmosphere and store it for decades — planting trees is great for this. We also should not rule out crazier solutions, such as adding reflective particles to the atmosphere that reflect sunlight and cool the Earth — so-called climate engineering.

What’s next?

We may get a reprieve next year but the outlook is generally more of the same but hotter.

Chris Rapley, professor of climate science at University College London: “We can anticipate big problems and costs ahead for all of us”

Chris Rapley

Chris Rapley

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Why are we seeing such a global trend? 

Climate scientists concluded decades ago that humanity has upset the energy balance of the planet by adding greenhouse gases to the atmosphere, mainly through burning fossil fuels. This was the unwitting impact of creating our current prosperity. Since the industrial revolution, and mainly in the last 30 years during what is called “The Great Acceleration”, the carbon dioxide content of the atmosphere has increased by the same amount as the natural change between an ice age and an interglacial warm period (when global temperatures shift by about five degrees Celcius) – but at a rate at least 100 times greater than in the natural cycles – and in a ‘warm’ direction not experienced by the planet for many million years. 

Most — roughly 94 percent — of the energy imbalance goes into the oceans which cover 70 percent of the planet’s surface and are dark. We measure this directly but also via sea level rise, which is measured from radars on orbiting satellites, as well as the worldwide network of tide gauges. Sea level is currently rising at 30 to 40 centimeters a century, which is a significant fraction of the sustained rate during the transition from the last ice age, when, due to the melting of the ice sheets, the sea level rose 120 meters. The sea level was stable for the last 2,000 years and is now accelerating — so in 100 years we humans have kicked off a global impact of geological proportions. 

The rising level is equivalent to the expanding liquid in a traditional thermometer — the sea water expands as it warms — thus acting as a planetary thermometer revealing warming directly. The meltwater from ice sheets and melting glaciers (90 percent worldwide are in retreat) adds to this. The fact that most of the heat imbalance goes into the ocean means that it is not surprising that the current El Niño in the Pacific is "supercharged." The El Niño releases heat to the atmosphere, with worldwide consequences, so if the ocean has stored more heat it should be no surprise that the combination of the El Niño and global warming should lead to the global temperature records we are experiencing.

Could 2016 become the hottest year in history?

Yes, based on the first months the probability is very high — almost certain.

Is it concerning?

Yes, of course! We have built the modern world — all its infrastructure, agriculture, water supplies, transport systems — based on the climate system we inherited. We are imperfectly adapted even to that — just look at the regular nature of ‘disaster’ stories of droughts, fires and floods — so it is imprudent to provoke the climate system into a new state to which we will be even less well adapted and much less robust.

Will something change in our lives? 

We are seeing change already. Climate change is acting as a "threat multiplier" making bad situations worse. For example, the megadrought in Syria between 2007 to 2010 is estimated to have been the one in a thousand year event — and a factor two to three times more likely as a result of the global warming we have experienced to-date. It displaced 1.5 million people from the land to the cities, to join the 2.5 million displaced by the Iraq war. So, climate change almost certainly exacerbated the flow of refugees to Europe (note: it did not cause the unrest or the flow — it made them worse). 

The prediction of climate scientists and indeed the World Economic Forum is that the involuntary displacement of very large numbers of people is the "new normal" — not some temporary "blip" — and climate change will be a growing contributing factor. Add in the direct costs and impacts on supply chains, insurance premiums and investment portfolios etc. of heat waves, droughts, floods, sea level rise and extreme events and it’s not difficult to see why the analysis of economist Lord Stern shows that from an economic point of view, as well as a humanitarian one, it is better to invest to avoid more climate change rather than to try to manage the unmanageable downstream.

What can we do? 

As individuals we can control our private lives and reduce our impact on the planet, according to our conscience (it must not become a tyranny; we are all embedded in a high carbon world not through our choice, but we can each make a small difference). We can also have an influence in our professional lives and companies will find they not only save money but even that staff morale and performance increase, as everyone is proud to work in an organization that demonstrates integrity and wider values than just the bottom line. 

But most of all, those of us who are privileged to live in democracies can express our views to our politicians, who take a short-term view and try to avoid policies that they see as potentially controversial — especially if these upset lobbyists and vested interests.

What can we expect to see in the future?

We see energy companies struggling to face the realities — some still haven’t got the message — other innovative companies such as Tesla are paving the way, as are the Chinese who are world leaders in solar power technology and related investment and have made impressive commitments to reduce carbon emissions and air pollution. But unless the scale and urgency of action are raised massively, we can anticipate big problems and costs ahead for all of us.

— By Dmitry Belyaev