So after a nice Christmas and New Year's break from blogging, here's my penultimate post about the 2 degrees scenario. Keep in mind the whole focus of this blog is on the potential effects of 2°C of warming on the ability of humans and other organisms to live on Earth. Let's jump right in.
Health:
Epstein (2000) and his evocative paper "Is Global Warming Harmful to Health?", as well as countless other papers and studies on health impacts of an increase in mean global temperature, show that this concern is growing. Epstein stipulated that warming would likely lead to an expansion of the incidence and distribution of many serious medical disorders. As mentioned in the previous post, this could be due to increased extreme events such as flooding or heatwaves, as "disasters promote by various means the emergence, resurgence and spread of infectious disease". Diseases relayed by mosquitoes in particular (malaria, dengue fever, yellow fever etc.) are likely to grow more concerning as changing climate leads to ripe conditions for mosquito breeding (namely stagnant water and warm weather). Interestingly, Epstein explains that the El Niño Southern Oscillation could be used to investigate the predicted future warming, as El Niño years result in changes to meteorological conditions not dissimilar to those predicted under climate change. As such, the 1997-1998 El Niño year, which has been highly studied, showed an increase in disease outbreaks. Epstein implies that this change can be inferred for gradual warming under climate change. Therefore, areas vulnerable to these diseases may see migration and a reconsideration of the habitability of the area.
Biodiversity:
To move slightly away from humans for a brief moment, global warming of 2°C is likely to have severe impacts on biodiversity (see Joe's excellent blog on flora and fauna). The IPCC estimates that 20-30% of animal and plant species will be at "increasingly high risk of extinction" as a result of exceeding 2°C of warming. As mentioned a few posts ago, coral reefs are highly vulnerable, and the IPCC estimates that even 0.5°C of warming could harm coral ecosystems. As warming increases to 2°C and beyond, more and more ecosystems become affected. Notably, at 2.5°C warming, there is predicted to be "major losses of Amazon rainforest", which leads to further depletion of carbon-absorbing sources (AKA trees), and increased difficulty of removing carbon from the atmosphere.
A large component of biodiversity is the amount of habitat available for the multitude of species on Earth. And the Committee on Climate Change suggests that over 20% of plant species and approximately 10% of animal species would experience over 50% habitat loss with 2°C of warming.
Hazards:
In particular, the risk of wildfires will increase as a result of a warming of 2°C. Warming World: Impacts By Degrees claim that, with each 1°C of warming, there will be 200-400% increases in the area burned by wildfire in parts of the western United States.
Loss of ice:
In particular, many studies claim that the Arctic may be completely ice-free due to global warming in the future. Day et al. (2012) suggests that 70-95% of sea ice loss in the Arctic is likely to be due to man-made greenhouse gas emissions. While this may be a controversial claim, scientists are no doubt in agreement about the loss of ice from the Arctic over the last 50 years, potentially of up to 30% annually. An important feature of the Arctic is also the permafrost that covers a large majority of the land. Because permafrost stores carbon from dead plants, and it is estimated that Arctic permafrost holds 1.7 trillion tons of carbon (more than all human activity has generated since the start of the Industrial Revolution), as warmer temperatures thaw the permafrost, huge releases of carbon dioxide and methane could occur. There has been great speculation as to the probability and potential damage of large releases of methane from Arctic stores and if interested, I would urge you to read Rob's great post about methane hydrates.
Food:
As mentioned in previous posts, food security is a looming concern in the face of future (and present) climate change. As the population continues to grow, feeding all the people in the world under changing climatic conditions becomes more and more difficult. Challinor et al. (2014) suggest that, without adaptation measures, 2°C of warming would result in losses in aggregate production for wheat, rice and maize in both temperate and tropical regions. Although there is still a lot of uncertainty surrounding the amount of production loss, some studies agree that warming temperatures would adversely affect agricultural production, particularly in the tropical regions. Some estimates include: 5-15% of yields of crops currently grown (Warming World: Impacts By Degrees) and 10% loss of maize and 15% loss of wheat (Committee on Climate Change). Interestingly, the IPCC argue the opposite, that 2°C (and up to 4°C) of warming would lead to positive crop yields. Ultimately, crop yields around the world will likely experience both gains and losses and it is still uncertain whether the Earth as a whole will experience net gain or net loss.
There are many more areas that 2°C of warming could impact but this was a brief introduction to some of the most concerning areas. All of these areas can affect human (and other organism) life and create obstacles for living safely on Earth. I hope you will agree with me when I say that it is obvious for our interest that we stay within 2°C of warming (or overshoot slightly and return below 2°C) by 2100 and for the foreseeable future.
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