In a session that swung wildly from specific questions on interest rates to whether climate change is an environmental or economic issue, Federal Reserve chair Janet Yellen was questioned pretty thoroughly today by the Senate.

Yellen will be back before the US Senate banking committee tomorrow.

The Fed chair was grilled on the course of rates, the appropriateness of the Fed’s forecasts, and the path for the central bank’s balance sheet.

Here’s what we learnt from Yellen today.

Is a March rate hike live?

Yes, just about. But only if the economy shows sufficient strength, of course.

Yellen did not say if Fed policymakers expected the economy would warrant three interest rate increases this year, as they last signalled in December.

Nor did she give a firm indication whether the first rate hike of the year might come in March or at the subsequent June meeting, which is when most analysts expect a rate increase.

However, she did say the Federal Reserve will likely need to raise interest rates one of the meetings coming up in soon, although Yellen flagged considerable uncertainty over economic policy under the Trump administration.

She said delaying rate increases could leave the Fed’s policymaking committee behind the curve and eventually lead it to hike rates quickly, which she said could cause a recession.

In prepared remarks, citing the central bank’s expectations the job market will tighten further and that inflation would rise to two percent, she said:

“Waiting too long to remove accommodation would be unwise.”

“At our upcoming meetings, the committee will evaluate whether employment and inflation are continuing to evolve in line with these expectations, in which case a further adjustment of the federal funds rate would likely be appropriate.”

Yellen was appearing in Congress for the first time since Republicans took control of the White House and both houses of the legislature and she nodded to the uncertainties over the direction of US economic policy.

On immigration

Immigration helps boost the labour force, a key component of economic growth, Yellen said.

“Immigration has been an important source of labor force growth.”

Likewise, slowing immigration would slow the pace of economic growth, she added.

President Donald Trump has called for stricter border controls and immigration enforcement to keep out undocumented workers, who he said unfairly compete with Americans for jobs.

On climate change

Senator Brian Schatz pressed Yellen on the Fed’s response to climate change.

She said:

“In monetary policy making our focus is on trying to achieve a strong labour market and price stability and our forecasts usually go out over a few years, but not over the decades in which climate change plays a role in affecting the economic outlook.”