Humans have long modified and changed the environment around them. For example, the rise of agriculture, favoring and cultivating certain plants and animals over others, led to reliable food supplies. Agriculture needed reliable water supplies which led to the diversion of rivers and irrigation. There are untold other changes, but until relatively recently in human history these changes were local or regional in nature. Case in point, the level of global CO2 emissions through most of human history were minimal and fairly consistent, largely from the burning of wood and some coal. Notice the line indicating CO2 emissions is barely discernible until roughly the 1850s. The explosion in industrialization levels changed all of this.
Even then emission levels largely continued to be from solid fuels: coal, wood, etc. Then, notice the rise of gas fuels starting in the early 1900s that coincides with the rise of cheap, mass produced automobiles such as the Model-T. Emissions from other fuel types really took off after World War Two. Gas fuel, gas flaring and cement production went from negligible to significant contributors to emissions. Surprisingly, cement production is a major cause of CO2 emissions. Cement is a vital part of a huge variety of construction activities. The primary ingredient of cement is limestone. The heating of limestone in the cement manufacturing process results in a significant release of CO2. It's also an energy intensive process that requires the burning of large amounts of coal and oil to manufacture.
The result of this explosive rise in emission levels, particularly in the 20th and 21st centuries, has led to large changes in the concentration of CO2 levels in the atmosphere. Even if CO2 emissions were suddenly reduced to zero it would still take centuries if not millennia for CO2 concentrations to fall back to pre-industrial levels. Historically the CO2 level since the rise of human civilization has been roughly about 280 parts per million in the Earth's atmosphere. They're now over 400 parts per million with a consequent rise in world temperatures and a decline in such things as world sea ice levels, particularly in the arctic.
Methane levels have been rising in concert with CO2 levels. While not as plentiful, nor as long lasting in the atmosphere as CO2 methane is a much more potent greenhouse gas, trapping 25 times more heat than an equivalent amount of CO2. The rise in methane levels can be attributed to some of the same causes as CO2, such as natural gas production. Some large, if unusual causes of increasing methane levels are trash rotting in dumps and livestock flatulence, particularly from cows. All told it's taken barely 30 years to raise methane levels by almost 200 parts per billion in the atmosphere.