Hello Anony Mous. I notice you wrote the following. "The book you spoke of was written in the 70s, we are now
50 years further and we’re still talking about 2.5C in the next 30 years
and the change since 1970 has been minimal, 0.5C with the predicted 1C
change being extended from 1980s to now 2050." That is somewhat a different impression than what I got from the book. The book was copyright in 1977 and it said "[m]ajor policy decisions will have to be taken" within 30 years from 1977, thus by 2007, to prevent serious problems by 60 years from 1977, thus by 2037.
Notice the book also said the following. "The results of global warming of 2.5°C, the anticipated outcome of
a dramatic rise in the carbon dioxide level within sixty years, are
virtually unimaginable.Major policy decisions will have to be taken with the next thirty years if this prospect is diverted." The book thus said the major problems would happen by the year 2037 (1977 + 60 years) if not enough is done by the year 2007. Nations have taken some actions by 2007 and some further actions were from 2008-2021, to avert the problem which the book says will happen by the year 2037 if not enough major action is taken. The actions which have been done have not stopped the warming, but they might have bought us some time in delaying a warming of 2.5 degrees Celsius above 1977 levels.
When scientists today talk about averting 2.5C increase they don't mean a 2.5 degree Celsius from today's temperature, but rather from a level prior level. They mean from above pre-industrial levels. The target level to avoid has thus not moved, though some say that even a smaller increase is dangerous.
See https://www.reuters.com/business/cop/whats-difference-between-15c-2c-global-warming-2021-11-07/ which says the following. "The 2015 Paris Agreement commits countries to limit the global average
temperature rise to well below 2°C above pre-industrial levels, and to
aim for 1.5°C. ... Already, the world has heated to around 1.1°C above pre-industrial
levels. Each of the last four decades was hotter than any decade since
1850." Notice that is says the temperature has already raised to
1.1°C above pre-industrial
levels.
Similarly https://www.ipcc.ch/sr15/faq/faq-chapter-1/ says the following. "At the 21st Conference of the Parties (COP21) in December 2015, 195 nations adopted the Paris Agreement2.
The first instrument of its kind, the landmark agreement includes the
aim to strengthen the global response to the threat of climate change by
‘holding the increase in the global average temperature to well below
2°C above pre-industrial levels and pursuing efforts to limit the
temperature increase to 1.5°C above pre-industrial levels’.
...Summary: Human-induced warming has already reached about 1°C above pre-industrial levels at the time of writing of this Special Report. By
the decade 2006–2015, human activity had warmed the world by 0.87°C
(±0.12°C) compared to pre-industrial times (1850–1900). If the current
warming rate continues, the world would reach human-induced global
warming of 1.5°C around 2040.
... In the decade 2006–2015, warming reached 0.87°C (±0.12°C) relative to
1850–1900, predominantly due to human activity increasing the amount of
greenhouse gases in the atmosphere. Given that global temperature is
currently rising by 0.2°C (±0.1°C) per decade, human-induced warming
reached 1°C above pre-industrial levels around 2017 and, if this pace of
warming continues, would reach 1.5°C around 2040.
While the change in global average temperature tells researchers about
how the planet as a whole is changing, looking more closely at specific
regions, countries and seasons reveals important details. Since the
1970s, most land regions have been warming faster than the global
average, for example. This means that warming in many regions has
already exceeded 1.5°C above pre-industrial levels. Over a fifth of the
global population live in regions that have already experienced warming
in at least one season that is greater than 1.5°C above pre-industrial
levels."
The Reuters' article I quote from above also says the following.
'So far, the climate pledges that countries have submitted to the United Nations' registry of pledges put the world on track for 2.7°C of warming. The International Energy Agency said Thursday that new promises announced at the COP26 summit - if implemented - could hold warming to below 1.8°C, although some experts challenged that calculation. It remains to be seen whether those promises will translate into real-world action.
Warming of 2.7°C would deliver "unliveable heat" for parts of the year across areas of the tropics and subtropics. Biodiversity would be enormously depleted, food security would drop, and extreme weather would exceed most urban infrastructure's capacity to cope, scientists said.
"If we can keep warming below 3°C we likely remain within our adaptive capacity as a civilization, but at 2.7°C warming we would experience great hardship," said Mann.'
The book from 1977 (and thus despite being 45 years old), in regards to what I quoted from it about climate change, is thus very much in agreement with what climate scientists are saying today.
