Earth’s climate is getting warmer, on average. But what does this really mean? The climate can vary from year to year – some years are hotter or colder than others, which can make it hard to determine how much the climate has changed. So in a unique approach to climate projections, Mora et al. (Mora et al. 2013. Nature 502:183-187) projected when year-to-year variability in Earth’s climate would exceed the historical boundaries of global climate. In other words, they asked the question: in which year will all subsequent years be warmer than what has been observed before 2013? The answer to this question is called the ‘year of climate departure’, where every new year will have break current climate records. If we look at the ‘business as usual’ scenario, the year of climate departure will be as early as 2047. Prior to 2047 however, most years will be record-breakers. The good news is that this is the worst-case scenario. If everyone were to pull up their socks and reduce their carbon footprint, reduce clear-cutting of forests, and use carbon capture technologies, the year of climate departure could be pushed back by a few decades to 2069. These predictions are considered ‘robust’ to error because the authors used 39 different climate models to obtain these results. Each model has different assumptions, and so if you use only a single one, the prediction may be incorrect. But if you use a lot of models, then the of all the predictions is less likely to have error due to having models that make different assumptions (and so as a whole, using all the models makes up for the individual assumptions of each model).
So what? Why are these results alarming? Well the year of climate departure is different for different places on the planet, and the tropics are very vulnerable (not to mention a lot of people live in the tropics). So if we look at how many people will be affected by an altered climate, even in our best case scenario, at least one billion people will be affected by 2050 – in the worst case scenario, five billion people will be affected by 2050. Hang on though, aren’t we expecting there to be more people in 2050 anyways? So it might just be the same proportion of people (but there are just more of us). Well no, those numbers are people who currently live in those areas. This means that if we continue along and maintain the status quo, most people on the planet will be afflicted with record breaking temperatures every year! On top of that the coral reefs, which are very sensitive ecosystems, have a year of departure of 2034 – in 20 years the coral reefs will likely look way different than they do today!
This study was a wake-up call: biodiversity and human society are threatened by climatic change, and this change is occurring faster than we previously thought. We notice yearly differences in temperature – when we have a warm winter or cool summer – and global climate change will become very easy to feel for those of us around in 2050. Every year will be record-breaking heat compared to now. Every. Year.
I would like to move away from those alarmist statements however with some good news. Life evolves and adapts. While rapid climate change may cause short-term issues (on the scale of decades to centuries), the biosphere will respond, and life will go on. Further living things can acclimatize to new environments (within reason), which is why 5°C feels cold in the summer but warm in the winter. So as long as we can find enough food and water, we will survive – the world will just be a different place.
Stay safe and stay informed,