A peek into the future

After realizing climate change is real and that we are its dominant cause, the next question is to find out how dangerous it is.

IPPC projections

The future of climate change not only depends on the present and the dynamics of the environment, but also on future emissions made by us. This is why four possible emission scenarios are considered: Representative Concentration Pathway (RCP) 2.6, RCP 4.5, RCP 6.0 and RCP 8.5, being RCP 8.5 the most dangerous option.

The following image from AR5 describes (a) the future anthropogenic radiative forcing considered for each possible pathway, (b) their components in terms of their radiative forcing, (c) their components as the percentage of the total radiative forcing:

The result is the following:

Since 1996, the EU is anouncing we should not let global warming overpass 2°C above pre-industrial revolution (Randalls, 2010). However, we are already at 0.8°C above pre-industrial temperature, and as you see in the projections above, we have to significantly reduce our carbon emissions immediately if we want to stay beneath that boundary. In fact the IPCC states we have to completely phase out fossil fuel emissions by 2100 if we do not want to suffer an extreme and irreversible climate catastrophe.

Impacts of global temperature increase:

We will give a short summary of some of the most important points. Impacts are deeply discussed in the IPCC reports, and for more details you should read the AR4 or AR5. All information below, except otherwise stated, is taken from the AR4.

• The proportion of land in extreme drought conditions is projected to rise from a current 1% to 30% in 2090.

• "The number of extreme drought events per 100 years and mean drought duration are likely to increase by factors of two and six, respectively, by the 2090s (Burke et al., 2006). "

• The water quality will significantly deteriorate leading to an important rise in health issues. 

• By 2100, the combination of increased humidity and increased temperature will threaten food growth, and therefore food prices are expected to significantly rise. This will have as a consequence a rise in diarrhoeal diseases and malnutrition in low income populations. 

• Rise in malaria, dengue and other infectious diseases. Rise in respiratory and cardiovascular diseases.

• If we reach an increase of 1.5-2.5 °C, 20-30% of species  are expected to be extinct. If we excede 3.5 °C, the number rises to 40-70% of species to be extinct.

• Ocean acidification: It is estimated that from one half to one third of the CO2 emitted after the industrial revolution was absorbed by the ocean. This means it acts as the biggest CO2 sink. CO2 absorbed by the ocean lowers the pH of the water, and it has decreased from 8.19 to 8.05 from industrial revolution (30% increase in terms of the acidity, because remember the pH scale is logarithmic). Ocean pH is expected to decrease in 0.5 units by 2100 in the ocean surface. This affects the ability of water animal's blood to carry oxygen, therefore affecting their growth and reproduction. In addition, 30% of warm water coral reefs have dissapeared since 1980, and models project the total extinction of reefs. This has major consequences because of the enourmous amount of animals that feed on them. 

          The following image from IPCC AR4 sumarizes the projections for species and ecosystems:

• By 2081-2100, there is to be an expected 0.45-0.82 m rise in sea level. Therefore, the coastlines will significantly change and low lying areas are threatened by the general sea level rise or by floods. A significant economic loss is projected.  

The following image briefly synthesises the IPCC projections for each of the paths clarified earlier:

Source: IPCC

Probably the best and more illustrative column in the table above is the one that indicates the percentage of emissions we have to reduce by 2050 to be at the indicated category, and the consequences. It clearly illustrated that to avoid overpassing a 2 degree change we need to lower the CO2 emissions by 72% to 41% by 2050. However, China stated they are going to peak emissions in 2030... So that is a very high aim to achieve. 

So...

I consider all of this overwhelming, and sufficient evidence to affirm this is an urgent matter, and something must be done if we do not want to continue through the RCP8.5 path. Additionally, these changes we need to make take a long time to be established, and therefore we need to act NOW. 

In following entries we will address possibilities of things to be done, to answer the question:

Is there any hope? 

I leave you with the sad cartoon of the day:

See you later!!!  :D