Markets cheer Greece's proposals to avert default; Nifty opens above 8,250: Markets have started the session on a higher note tracking positive trend among global peers. By 9:30, the Sensex was higher by 168 points at 27,484 and the Nifty gained 53 points at 8,278. Market participants will keep an eye on how the monsoon progresses. The June-September southwest monsoon is critical for the country's agriculture because a considerable part of the country's farmland is dependent on the rains for irrigation. Global events such as Greece outcome could also drive the markets. Further, stock markets may witness volatility this week amid expiry of derivatives contracts.