The climate is described by the laws of Physics and Chemistry. And also Biology. These have NOT changed. The phenomena have not changed. The dynamics haven't changed. What may have changed are the inputs: more CO2 emissions, more CO2 and methane emitted by the biosphere, more intense solar radiation.

If the weather is a dynamical system, it is (by definition) always changing. Moreover, "change" only means things are not static. It does not quantify how much things have become different. Better call it a crisis because the measures being proposed to fight the problem suggest that, indeed, this is a crisis.