Your question is very important to answer. I want to answer it because I have been interested in and worked on managing the interaction of people with the Earth for as long as I can remember. At your age, I was asking what the world was like before people and what difference we have made, good and bad. What a tough question. And 1.5 degrees does not seem like much, does it? Your question is so important that the Intergovernmental Panel on Climate Change (IPCC) devoted a whole special report of 630 pages in 2018 to this question. The answer I give is only a snippet of what you might wish to learn.
What does it mean to have a 1.5 degree Celsius temperature rise? This means that the average surface temperature (across all land, sea, and ice) of the Earth will have risen by 1.5 degrees since pre-industrial times. Pre-industrial times were times when the impacts people had on the Earth were very small and local to where they lived.
Because this is the average whole-Earth-surface temperature increase, the increase in average temperature will be different in different places – hot, dry areas will become hotter and drier. Cool, wet areas will become warmer and may either become drier or wetter depending on where they are. Frozen areas will become ice-free. The tropics will become places difficult to live in, for people, animals, and plants. The polar environments will reduce and may disappear in some places. This is happening now with the bleaching of coral reefs, the burning of rainforests, the drying of the continents and the reduction of ice-dependent systems, particularly in the Arctic and in the highest mountain ranges. And the sea level is rising. Thus, an average increase of the Earth’s temperature even before we reach 1.5 degrees can have wide ranging effects because of this variation around the Earth.
According to the IPCC, the Earth will not be doomed when the average temperature of the Earth goes past 1.5 degrees but, increasingly, life will become very different to what we are used to and, for many people, animals and plants, it will become very much harder to live (thousands of species are expected to go extinct as a result and many people will die). Our dreams and stories about life on the Earth will more and more become memories of past days rather than opportunities for experiencing in the future. But why would that be?
There are two very important factors to consider. The first is how rapidly and how far the sea level will rise. In Tasmania, many low-lying areas with townships (e.g. Kingston Beach) will become more frequently flooded, to the point when insurance companies will no longer insure houses for damage. Who will pay for those people to move their homes? Where will they go? More significantly, many low lying countries will become uninhabitable because of sea-level rise and floods. The people from those countries will need to move. How many millions of people will that be? Where will they go? Will they be helped to relocate? How understanding will the world be to people forced out of their homes?
The second factor is what a warmer atmosphere and ocean will do? Communities and livelihoods built on or around ice (permafrost, glaciers, snow) will reduce and possibly disappear. The IPCC has well established that the frequency and intensity of extreme weather events will increase. Increased storms and floods will compound the impacts of sea level rise as well as disrupt ports, coastal airstrips, roads, electricity grids and so on. But it is not just about storms and floods, it is also about heat waves and droughts. Hotter and longer heat waves will result in more people dying from heat stress. Longer and more frequent droughts will mean farms, grasslands and forests will become much drier and more difficult to sustain. This will lead to starvation and lack of water in many communities. In Australia, our Great Artesian Basin that gives water to so many of our rural communities will begin to dry up. Some of the more sensitive areas will be lost, like the Great Barrier Reef.
Limiting warming to 1.5 degrees will give us a greater chance of restoring the world to what we know and love. The greater the Earth warms the longer the impacts of that warming will last – rather than the effects of warming remaining until the end of the century it is likely to remain long after that time. Many scientists fear that if the Earth warms beyond 2 degrees then it may reach tipping points from which we cannot return to what we know. How can we believe this will happen when we have not experienced these levels of warming? The IPCC has well established mathematical models able to assess the nature of the climate, weather and state of the physical Earth system. These models have been tested in many ways to ensure they can be validly used to assess what the world will be like. These models then are used to determine what might happen to farms, forests, cities and ocean systems. For Tasmania, this has been done in a Climate Futures Tasmania project, which was one of the first projects globally to undertake these kinds of assessments to help communities and governments better plan and adapt to the future.
Can you believe these results? Ask your parents or grandparents how reliable the weather forecasts were during their childhood. Compare that to the forecasts we have now when we can plan at least four days in advance for what the weather will be like. These forecasts are based on atmospheric models, the same kind of models used for climate assessments.