Ok, so we’re not really all going to die – not yet anyway – but the IPCC did release Part II of report number 5 last week and there’s lots in it which should be cause for concern. The first part – released last year – was about the science of climate change. This one is about Impacts, Adaptation and Vulnerability. Contributing to this report were 243 lead authors from 70 countries as well as 50,492 comments and over 12,000 scientific references cited.
I’ve been wanting to write something about it but thought I should read it first. However it’s very long and I may never read it in its entirety, so to steal the words of Sydney Smith:
I never read a book before reviewing it. It prejudices a man so.
I’ve skimmed the first 7 chapters and pulled out some important points but left many others. I’ll write about the other chapters in a subsequent post. This section is about the impacts of climate change on natural and managed resources.
Climate change will increase the frequency of droughts, floods, heat waves, tree mortality (already being observed) and forest dieback, and will negatively affect freshwater ecosystems. There will be more heavy rainfall events, glaciers will continue to melt and the frequency of landslides is expected to increase. Sea level rise (projected to be in the range of 0.28-0.98m by 2100) will contribute to flooding and erosion; storm surges will get worse; ocean acidity will increase as will the temperature of coastal water which is bad news for coastal ecosystems and the communities that depend on them. Coral reef ecosystems are particularly vulnerable and have few adaptation options.
There is increasing risk of species extinction and this has possibly already begun (e.g., central American frogs). Plants and animals will move towards cooler regions – the poles and higher altitudes – and in some cases are doing so already. But some species will not be able to move fast enough and some habitats may disappear altogether. Fish will continue to move towards cooler water which will be beneficial to some commercial fisheries at the expense of others and as always seems to be the case, it’s the poorest regions of the world that are the most vulnerable.
Some plants will grow faster with higher levels of CO2 – but only up to a point – and some will also use less water. But this enhanced growth will be at the expense of important nutrients resulting in poorer quality food. There is also some evidence that enhanced tree growth from increasing CO2 has already peaked in many places. Once the temperature hits 1°C above preindustrial (and we’re currently at about 0.8°), the yields of major crops – wheat, rice, maize – are projected to be negatively affected (although some regions may individually benefit). Hot nights are already having an impact on rice yields and rice quality.
Warmer temperatures are causing invasive insects to spread, like the mountain pine bark beetle. Spring events like breeding, budding, flowering and migration are changing and starting earlier. Climate change has also contributed to the spread of viruses and ticks that affect livestock.
Ecosystems in the tropics and the high latitudes are particularly at risk. In the tropics this is because the plants and animals there have evolved within a limited temperature range and in many cases are already at their maximum limits. In the high latitudes, species are at risk because the projected temperature change will be large.
It’s possible that deserts will expand, despite increases in rainfall on the earth overall. They will also become hotter and dryer.
The Arctic is warming faster than the global average and this is affecting animals there. According to the report, seven of 19 subpopulations of polar bear are in decline, while four are stable, one is increasing and there’s insufficient data on the remaining. It is expected that their numbers will dramatically decline as the Arctic warms.
Frozen soils and permafrost hold more than twice the amount of carbon in the atmosphere. When they melt, they release carbon and methane and so present an additional threat and source of greenhouse gases.
The next six chapters relate to humans so I’ll save those for next time.