An Introduction to Climate Change

An Introduction to Climate Change as it may affect Lincolnshire.

The first thing to try to understand about climate change is uncertainty. We are dealing with the future and we don’t quite know how that’s going to turn out.  What we can do is say things like “If we do such and such, then this is likely to happen”.

A first layer of uncertainty is what we, the humans, are going to do. People and their governments are unpredictable but how we behave over the coming years will be critical to the course of climate change. Every government policy that stops more coal, gas and oil from being extracted will slow down the rate of global heating, and every action we as individuals take to reduce our personal carbon footprints also makes a difference.

“What I do won’t make much difference” said eight billion people.

To show what people might do, the IPCC described some scenarios based on how much greenhouse gas we emit in the coming decades, and how much global warming each of these scenarios is likely to produce by year 2100. If we all stopped burning fossil carbon by tea-time tomorrow the temperature could stay below 2°C above 19th century levels. But that’s not going to happen! If every nation takes drastic action, as they have promised, then warming could be limited to only a little over 2° but if we carry on with ‘business as usual’, even if we phase out greenhouse gas releases after mid-century, then a 3° or more warming by the century’s end is likely.

These numbers, projected temperatures following various policies and actions, are calculated by climate models. And here we have another layer of uncertainty. The figures above should properly be given as a range of values. For example, the scenario that the IPCC labels ‘RCP4.5’ (many people regard this as a likely scenario) gives a median value of 2.4° but with a range of likely values between 1.7° and 3.2°C of warming by 2100. That’s quite an uncertainty range; the end points of that range would feel very different.

But it gets worse. The climate models have actually turned out to be very good at predicting global heating so far. Ask the models to use the data from a decade or two ago to tell us what today’s situation is and the results prove to be very accurate. But we cannot have the same confidence in the models’ ability to tell us about the future. This is because conditions in the oceans and atmosphere have changed and will change further, in ways that we are unsure of, so our inputs to the models may turn out to be wrong. And that means the outputs, the predictions we are interested in, may also be wrong. Unfortunately, there is more scope for climate models to be wrong on the bad side than on the benevolent side.

Let’s nevertheless make the bold assumption that the models give us a good picture of the future. How would any particular level of global heating translate to the climate change we experience in Lincolnshire? More uncertainty! Those warming figures are for the average of surface air temperatures of the whole planet. Heating will be greater at the poles and less at the equator, with our latitude being just a little above the average. Our climate is strongly influenced by the surrounding seas and ocean. And here we find more uncertainty. The summer of 2023 saw a record high temperature in the North Sea and exceptionally warm seas right round the British Isles. It was probably the warmest water we’ve had since the Eemian age, over 100,000 years ago. Summer 2024 could be warmer still!

Will our seas continue to warm through the century? Not necessarily. There is a large scale circulating current of water in the Atlantic Ocean, called the Atlantic Meridional Overturning Circulation (AMOC), which brings warm water from the tropics poleward and returns cooler water towards the south. (The Gulf Stream is a part of AMOC.) This ocean current keeps North West Europe relatively warm, milder than the same latitude on the Canadian coast. (Shetland is the same latitude as southern Greenland.)

There is evidence that in recent years the AMOC has been slowing down and there are indications that it might stop altogether in the coming decades. Were that to happen, the British Isles could experience a rather sudden cooling, while the rest of the planet continued to heat up. But this is an area of scientific uncertainty; warmer or colder, it could go either way.

One thing we can be pretty sure about is that in a warmer world there will be more rain. Higher temperatures mean more evaporation from the oceans and more moisture held in the air. And what goes up, must come down. Unfortunately, rainfall distribution is likely to be uneven, with storms and spells of heavy rain at times but lengthy spells of dry weather, droughts, at other occasions. This aspect of our local climate change is amongst the area we may need to adapt to. We need to be able to cope with greater floods, but also ensure that our landscape retains water for use during drought periods.

If the AMOC does not slow down substantially and we retain our relatively mild oceanic climate, then a couple of degrees of average global warming may produce for us a climate more like that today found in central and western France. Mostly mild winters but with the possibility of sharp cold spells, and significantly hotter summers. Coningsby set a new high temperature record of 40°C in the summer of 2022, and that could become the new normal. The crops our farmers grow, the way we manage landscapes for wildlife, and the way we design our urban areas, may all need adjustment.

A warmer world means more energy in the atmosphere. While that might benefit the North Sea wind industry, it could also bring more frequent and more damaging storms. It might be wise to design our buildings and other structures with this in mind, able to withstand higher wind speeds than we have previously experienced.

A profound consequence of global heating is sea level rise. As the oceans’ waters warm, they expand slightly, but a larger contribution to sea level rise is now the melting of ice in Greenland and the Antarctic. While the East Antarctic Ice sheet is mostly still very cold, the Greenland and West Antarctic Ice Sheets are vulnerable. Together these two areas could contribute some 15 metres of sea level rise. It will be a slow process, perhaps taking centuries, but within the lifetimes of our younger folk there could be two metres added to the sea levels of Lincolnshire’s coast. Vital decisions will need to be taken regarding how much resource the nation invests in strengthening our sea defences and creating coastal realignment schemes. At some point a future generation will face the loss of the Lincolnshire Marsh and Fens.

Finally, we should consider an indirect effect of climate change, but one which could affect us profoundly. While our oceanic climate ameliorates the most extreme consequences, a 2° or more warmer world will create a vast swathe of land from North Africa, across the Middle East and through Southern Asia, all but uninhabitable because of unsurvivable temperature peaks. A billion climate refugees will be on the move, some choosing Lincolnshire as a desirable destination. How the global economy and society are affected may turn out to be the biggest uncertainty of all.