Believing in climate change

Hello again!!

The other day I was speaking to my non-environmental friends, and when we discussed the importance of climate change they were really unconvinced about it. Some didn't consider climate change was a very big issue; others thought it is a natural process that has nothing to do with human activity. So, before analyzing if we can do anything to revert or stop climate change, I'm going to dedicate this entry (and probably the next one), to understand the importance of this subject.

The Intergovernmental Panel on Climate Change (IPCC) has affirmed in its AR5 that:

"Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, and sea level has risen."

Note: Since I will be using a lot of the IPCC statements and projections, I thought this might be a good time to clarify who they are. As their name suggests, they are an Intergovernmental panel of scientists working under the UN. Their reports intend to cover 

"the scientific, technical and socio-economic information relevant to understanding the scientific basis of risk of human-induced climate change, its potential impacts and options for adaptation and mitigation." 
(Source: Principles Governing IPCC Work)

I should also say that the IPCC doesn't carry out their own research but, rather, assesses all the existing literature and extracts conclusions from that. They are considered the authority on the subject, and that's why I'll be quoting them so much.
The IPCC is the organisation that shared the Nobel Peace Prize with Al Gore in 2007. 

Let's continue. There are ten parameters of the physical world that can prove the veracity of a global warming. These are synthesised in the following picture.

Source: NOAA

We will give the details for just a few of these indicators, but it should be noted that all of these parameters are changing in the direction that proves global warming is occuring.

• First, air temperature near surface. The average temperature has increased 0.6°C in the last 30 years. If we consider the last 100 years, the global change would be of 0.8°C. This can be seen in the graph below: 

Image showing annual mean temperatures and 5 year mean temperatures since 1880. Taken from Hansen et al. (2006)

• Second, we can observe changes in the snow and ice covered area. The Arctic sea ice extent has decreased at an average annual rate of 2.8% per decade since 1978. Additionally, the graph below shows the decrease in snow covered area since 1920 in the northern hemisphere. 

Source: IPCC AR4

• Third, the global average sea level has grown at an average annual rate of 1.8mm per year from 1961 to 2003. However, if we only consider the average from 1993 to 2003, the average sea level rise would be of 3.1mm per year. 

Source: IPCC AR4

Something that really surprised me is the main reason of sea level rise, and therefore I consider worth mentioning it. According to IPCC, the ocean's "thermal expansion" is responsible for 57% of the global sea level rise. The ocean has always acted as a buffer with global temperature, absorbing or releasing heat according to the global temperature. So "thermal expansion" is the expansion produced by the absorption of heat by the ocean. The following graph shows the evolution of this magnitude in the last 50 years in the upper 2000m of the ocean.

Source: NOAA

Apart from considering these formal indicators, we can observe other global change characteristics of the Earth like the following ones taken from IGBP Global Change. In this webpage you can find evolution graphs for almost everything in the world, and I recommend you check it out!
I chose the three I liked the most. Or rather disliked, for what they represent.

Number 1: tropical rainforest and woodland.

Number 2: ozone. Really amazing numbers. No wonder exposures to the sun are getting dangerous. Besides this first consequence, you can get a list of impacts of ozone depletion here.

Number 3: species extinctions. My heart broke when seeing this. Maybe you will share my sorrow for ruining the planet not only for ourselves, but for other species that were living here long before us.

It should be noted that these three are indicators of global change, and not necessarily of global warming. Still, the evidence that they are anthropogenic is staggering. Thus, correlation is established, if not causality.


Number 4: I leave you with the final and most important evidence:

Dave Granlund :)

SUMMARY: climate change is REAL, the evidence is really unequivocal.

In our following entry we will discuss the main causes of climate change. See you soon!

:D