The two brothers behind the petition, Nick and Simon Aldridge were not the people who collected and analysed the climate data, but respected scientists who understand how climate works. They examined ice cores going back thousands of years, widths of tree rings, ancient weather records, recorded earthquakes and amounts of ice formation, and more.
They calculated that the range of temperatures which were conducive to the development of the earth's various climatic regions, and the evolution and continuing success of vegetable and animal life in them, were surprisingly narrow. A few degrees in either direction and we might never have been here at all.
The inescapable conclusion from what they found from the cycles of natural phenomena was that we were actually due to move into another ice age, not an age of global warming.
The factor that seems to have made the difference is the amount of Co2 and other gases that are released by modern human beings as they alter their environment to suit their concept of what is necessary to fulfil their lives. That includes built-in obsolescence in their homes, factories, cars, clothes, food, communication technology, entertainment, holiday destinations, planes. Goods are not used and reused until they fall apart, they are replaced by "better" versions and the older ones buried in landfill.
All these material objects are produced or powered or transported by energy. Before the Industrial Revolution, the energy to make these things came from human beings farming by hand, or horses pulling ploughs or carts, or blacksmiths wielding hammers in a forge, or women spinning thread to weave cloth. With the machines invented to make production easier and quicker, more input of energy was needed to keep the cogs turning to produce the goods needed by an expanding population expecting more of life than just surviving another hungry winter. Faster and easier production meant that people owned more, ate better, and their children survived their childhood to reproduce and need even more food and more possessions. The global population has grown from 1 billion in 1800 to 8.2 billion in 2025 ( www.worldometers.info/world-population/ - see the number rise as you watch!) and the amount of greenhouse gases has risen exponentially with them.
Energy is produced by fuel - oats, grass and hay for horses, decent food for humans, and fossil fuels (coal and oil) and electricity for machinery. When coal and oil burn, they produce gases - the carbon dioxide that was trapped in the trees and vegetation that formed them, and others too. These gases blanket the earth and keep the heat that rises from the land that is warmed by the sun from rising above the atmosphere and dispersing.
Nasa has more info on the causes of climate change, but the takeaways from their (very readable) webpage are:-
The greenhouse effect is essential to life on Earth, but human-made emissions in the atmosphere are trapping and slowing heat loss to space.
Five key greenhouse gases are carbon dioxide, nitrous oxide, methane, chlorofluorocarbons, and water vapor.
While the Sun has played a role in past climate changes, the evidence shows the current warming cannot be explained by the Sun.
science.nasa.gov/climate-change/causes/