What is the IPCC?
The Intergovernmental Panel on Climate Change was made in 1988 by the WMO and the UNEP as a group to make reports of the scientific and socio-economic risks of man-made climate change, and options to adapt or mitigate against it. 
It’s work is split up into 5 groups :
- Working Group I (WGI) gives the scientific information needed to understand climate challenges, assessing atmospheric changes, natural cycles and whether, and climate sensitivity.
- Working Group II (WGII) assesses the impacts that climate change can have on human cultures and settlements, and their vulnerabilities.
- Working Group III (WGIII) looks at mitigation methods, exploring how we can implement them – technical feasibility, costs, and prerequisites.
- The Task Force on National Greenhouse Gas Inventories (TFI) looks specifically at measuring greenhouse gas (GHG) emissions for each country, such as developing methods and software that everyone can agree upon.
- The IPCC Task Groups are set up to deal with specific issues at the time, and right now there are four active. 
The IPCC reports
The biggest reports the IPCC produces are its Assessment Reports which involve all its groups, Special Reports which look at specific issues, and Methodology Reports, which help governments make GHG inventories. 
There are five Assessment Reports, which came out in 1990, 1992, 1995, 2002, 2007, and 2014. The sixth one (AR6) will be completed in 2022. 
Here is a quick summary of its most import reviews:
Assessment Report 5 (2014)
Assessment Reports are big. Huge. Just WGI’s contribution to AR5 is over 2000 pages long and the whole thing cites 9200 publications . Helpfully, all reports have summaries for each section, providing their own perspectives of the report’s findings.
WGI’s Summary for Policymakers (SPM) shows the observed changes in climate systems in the past, the drivers of climate change, models for the climate, and future changes in the climate due to human activity. For all of its claims based on models or predictions, WGI also give a likelihood that they are right.
These likelihoods depend a lot on the Representative Concentration Pathways (RCPs) and the models used, which you can find out more about here. In the main report, for example, when predicting how much sea ice will decrease in the Southern Hemisphere summer using one model, the decrease in permafrost can range between 37% and 81%. Either way, WGI is virtually certain that these decreases will occur – meaning they are over 90% sure. 
WGII’s SPM follows a similar pattern of exploring past observed human impacts and vulnerabilities while adapting to climate change, understanding where these are in future risks, and how to build resilience against them.
For example, they identify with medium confidence that global risks concentrate in urban areas, and with high confidence that climate change will cause more ill-health in the 21st century, especially in low income areas.
Very importantly, WGII states that emphasis of policy on short term outcomes leads to increase vulnerabilities, and that good adaptation cannot be achieved without mitigation.
Finally, WGIII’s SPM takes the scientific and socio-economic work of the last two and explores how to mitigate in the long term, the policies for nations and sectors , and the importance of international cooperation.
Very importantly, they found that mitigation is slowed by agents advancing their own interests. Being written in 2014 when the concentration of CO2 was about 397 parts per million (ppm) , WGIII claims it is likely that this number must be kept below 450 ppm before 2100 to limit warming to 2°C. As of April 2020, the concentration is already about 416 ppm .
The Climate and Development Knowledge Network (CDKN) has also made region specific summaries of the report, “What’s in it for…” Small Island Developing States (SIDS), Africa, South Asia, and Latin America.
Special Report: Global Warming of 1.5°C
This is another big drop from the IPCC, a 5 chapter special report on the impacts of warming 1.5°C above pre-industrial levels . The five chapters follow key themes in the Panel’s research aims:
- Chapter 1: the impacts of 1.5°C warming on sustainable development and poverty eradication.
- Chapter 2: the carbon budget and how emissions can be brought to zero by 2050
- Chapter 3: the importance of 1.5°C, and the dangers of going above it
- Chapter 4: weighing up adaptation and mitigation, and which has more feasible transitions
- Finally, chapter 5: interactions of both mitigation and adaptation with the other Sustainable Development Goal
This report brought many headlines when it was released in October 2018. Its key findings include that we are currently on track for 3-4°C warming and that meeting the target of ‘only’ 1.5°C warming would be possible but only with ‘deep emissions reductions’ and ‘rapid, far-reaching and unprecedented changes in all aspects of society’. The report further outlined the significant differences between an increase of 1.5°C and 2°C – the latter being much more damaging. 
The report found that limiting warming to 1.5°C would require a decrease in net emissions by 45% by 2030 and a net zero status by 2050. For a 2°C target, there would have to be a 25% reduction by 2030 and a net zero status by 2075.
However, what is key to remember is that the world is not on track to limit warming to 1.5°C or even 2°C – even if all current government pledges were fulfilled  . To do so would require immediate transformations, which may bring about very mixed outcomes. Take a look at ClimaTalk’s articles on mitigation limits and their economics. www.ipcc.ch/site/assets/uploads/2018/09/ipcc-principles.pdf
 www.ipcc.ch/about/task-groups/ as of 07/04/2020