Ay increase by more than 170% to meet the body's increased o2 demands. this increase in cardiac output increases blood pressure. but the accompanying increase in arterial pressure is relatively small—only about 40%. what limits this increase in blood pressure so that it doesn't reach dangerously high levels during exercis

I believe the increase in blood pressure is limited by the Vasodialtion that causes arterial diameter to increase in the exercising skeletal muscle.
 Vasodilation causes increase in blood flow due to decrease in vascular resistance. The resistance produced mainly in the arterioles which is known as the systemic vascular resistance or the peripheral vascular resistance. The cardiac output is the function of heart rate and stroke volume and must be always on check.

No because the eaeht is on a 23.5 degree axis tilt and so when it is winter the northern hemisphere is pointing away from the sun and the soutubern hemisphere is pointing toward the sun