A slow-arriving but steady upturn in California’s economy is beginning to translate into higher taxes paid to the state, pushing revenues collected this year more than $2.3 billion above projections made in January. The new money will erase part of the remaining $15 billion shortfall between what the state expects to spend and what it is likely to receive in tax payments over the next 14 months. But it is probably too soon to tell whether the infusion of unexpected cash is a sign that the economy is taking off or a merely temporary surge that could disappear as quickly as it arrived.